Diagnostic Imaging of Solitary Tumors of the Spine ... - RadioGraphics

Note: This copy is for your personal non-commercial use only. To order presentation-readycopies for distribution to your colleagues or clients, contact us at www.rsna.org/rsnarights.EDUCATION EXHIBITDiagnostic Imagingof Solitary Tumorsof the Spine: Whatto Do and Say 11019CME FEATURESee accompanyingtest at http://www.rsna.org/education/rg_cme.htmlLEARNINGOBJECTIVESFOR TEST 3After reading thisarticle and takingthe test, the readerwill be able to:■■Describe the commonfeatures ofspinal tumors.■■Develop a shortdifferential diagnosisfor patients with spinaltumors.■■Discuss the roleof radiography, CT,and MR imaging inthe diagnosis of spinaltumors.TEACHINGPOINTSSee last pageMathieu H. Rodallec, MD • Antoine Feydy, MD, PhD • FrédériqueLarousserie, MD • Philippe Anract, MD • Raphaël Campagna, MDAntoine Babinet, MD • Marc Zins, MD • Jean-Luc Drapé, MD, PhDMetastatic disease, myeloma, and lymphoma are the most commonmalignant spinal tumors. Hemangioma is the most common benigntumor of the spine. Other primary osseous lesions of the spine aremore unusual but may exhibit characteristic imaging features that canhelp the radiologist develop a differential diagnosis. Radiologic evaluationof a patient who presents with osseous vertebral lesions oftenincludes radiography, computed tomography (CT), and magneticresonance (MR) imaging. Because of the complex anatomy of the vertebrae,CT is more useful than conventional radiography for evaluatinglesion location and analyzing bone destruction and condensation.The diagnosis of spinal tumors is based on patient age, topographicfeatures of the tumor, and lesion pattern as seen at CT and MR imaging.A systematic approach is useful for recognizing tumors of thespine with characteristic features such as bone island, osteoid osteoma,osteochondroma, chondrosarcoma, vertebral angioma, and aneurysmalbone cyst. In the remaining cases, the differential diagnosis mayinclude other primary spinal tumors, vertebral metastases and majornontumoral lesions simulating a vertebral tumor, Paget disease, spondylitis,echinococcal infection, and aseptic osteitis. In many cases, vertebralbiopsy is warranted to guide treatment.© RSNA, 2008 • radiographics.rsnajnls.orgAbbreviations: ABC = aneurysmal bone cyst, H-E = hematoxylin-eosin, SAPHO = synovitis, acne, pustulosis, hyperostosis, osteitisRadioGraphics 2008; 28:1019–1041 • Published online 10.1148/rg.284075156 • Content Codes:1From the Department of Radiology, Fondation Hôpital Saint-Joseph, 185 rue Raymond Losserand, 75674 Paris 14, France (M.H.R., M.Z.); andDepartments of Radiology B (A.F., R.C., J.L.D.), Pathology (F.L.), and Orthopedics B (P.A., A.B.), Hôpital Cochin, Paris, France. Recipient of aCertificate of Merit award for an education exhibit at the 2005 RSNA Annual Meeting. Received July 11, 2007; revision requested August 9 andreceived October 9; accepted October 23. All authors have no financial relationships to disclose. Address correspondence to M.H.R. (e-mail:mathieurodallec@hotmail.com).© RSNA, 2008

1020 July-August 2008 RG ■ Volume 28 • Number 4TeachingPointIntroductionMetastatic disease, myeloma, and lymphoproliferativetumors of the spine commonly cause multiplelesions, which, in association with the clinicaldata, usually allow the diagnosis to be easilymade. In contrast, primary spinal tumors mustbe considered in cases of a solitary spinal lesion.A wide variety of primary neoplasms can involvethe spine. Spinal tumors can be classified accordingto their tissue of origin (Table). Patients’symptoms are often nonspecific.In this article, we review the clinical features ofspinal tumors and the use of various imaging modalitiesin the evaluation of these tumors. We thendiscuss and illustrate the imaging findings of primarytumors of the spine, with emphasis on theimportant role the radiologist plays at the timeof diagnosis in evaluating lesion topography andextension. The radiologic appearances of these lesionscan sometimes suggest a specific diagnosis,thereby helping guide our clinician colleagues inthe complex treatment of affected patients.Clinical FeaturesClinical data, such as patient age, symptoms,history, and laboratory findings, help make theradiologic diagnosis. A prior history of radia- tiontherapy suggests radiation-induced tumors.Some tumors have a predilection for specific agegroups. In patients under 30 years of age, tumorsof the spine are fairly uncommon and are generallybenign except for Ewing sarcoma and osteosarcoma(1). In patients over 30 years of age,most tumors are malignant except for vertebralhemangiomas and bone islands. Metastases arethe most common lesions. Sometimes, clinicaldata are so typical for a certain disorder that theyallow the final diagnosis. For example, in a youngadult patient, bone pain that occurs mainly atnight and is promptly relieved with salicylates ishighly suggestive of osteoid osteoma. In manycases, however, clinical data are not specific, withback pain being the most common complaint. Insome patients, initial symptoms may simulatedisk herniation. Vertebral fracture sometimesreveals spinal tumors. Radicular or spinal cordcompression depends on the location and extensionof the spinal lesion in the foramina andspinal canal. The growth rate of the tumor mayalso be a factor in differentiating high-grade malignanttumors (usually fast growing) from lowgrademalignant and benign tumors (usually slowgrowing).Classification of Primary Spinal Tumors byTissue of OriginOriginOsteogenicChondrogenicFibrogenicVascularHematopoietic,reticuloendothelial,lymphaticNotochordalUnknown*Extremely rare in the spine.TumorsBone islandOsteoid osteomaOsteoblastomaOsteosarcomaOsteochondromaChondroblastomaChondrosarcomaFibrous dysplasiaBenign fibrous histiocytoma*Malignant fibrous histiocytoma*HemangiomaParaganglioma*Epithelioid hemangioendothelioma(hemangiosarcoma)*Hemangiopericytoma*HistiocytosisPlasmocytoma, multiplemyelomaLymphomaLeukemiaEwing sarcomaChordomaAneurysmal bone cyst (ABC)Giant cell tumorImaging ModalitiesConventional radiography is complementary tomagnetic resonance (MR) imaging and computedtomography (CT) even if they play a lesssignificant role. CT and MR imaging are neededfor evaluation of both the intraosseous extent ofthe tumor and soft-tissue involvement. We havefound CT to be the most accurate method forevaluating the extent of osseous involvement andthe degree of cancellous and cortical bone loss.CT helps evaluate the risk for vertebral body collapse.MR imaging is the best imaging modalityfor the evaluation of the epidural space and neuralstructures. Nevertheless, weight-bearing fullspinex-rays may help the surgeon in making adecision regarding overall spinal balance and theneed for stabilization.Multidetector CT is performed in most caseswith a large field of view and no contrast medium.With an isotropic volume acquisition, it ispossible to obtain axial, sagittal, and coronal reformattedimages that are of the same quality asthe source images. Two-dimensional multiplanarreformatted images are useful in the evaluation

RG ■ Volume 28 • Number 4 Rodallec et al 1021Figure 1. Chart shows the common distribution oftumors of the spine.of cortical bone destruction and calcified tumormatrix.Our MR imaging protocol includes sagittaland axial images in all cases. Coronal images maybe helpful for the evaluation of paravertebral softtissueextension. T1-weighted images are helpfulfor delineating normal bone marrow architecture,fat content within masses, and subacute hemorrhageand for evaluating tissue enhancement afterthe intravenous administration of contrast materialcontaining gadolinium–diethylenetriaminepentaaceticacid. The administration of gadolinium-basedcontrast material results in enhancementproportional to soft-tissue vascularity andis helpful for differentiating cystic lesions fromcystlike solid masses. It is also useful for biopsyin that it allows differentiation of enhanced viabletumor from areas of nonenhanced necrosis.In addition, gadolinium-based contrast materialis frequently used to better demonstrate epiduralextension. Contrast material enhancement isbest evaluated on fat-saturated T1-weighted MRimages. Inhomogeneous suppression of the fatsignal can impair the quality of images obtainedin the cervical and thoracic spine because ofphase-encoded motion artifacts. Thus, contrastmaterial–enhanced non-fat-suppressed T1-weighted images are reliable and remain valuable.Dynamic contrast-enhanced MR imaging mayprovide information about the rapidity of theenhancement (2). Most pathologic processes areoften highlighted on T2-weighted images due totheir increased fluid content. T2-weighted imagesdelineate spinal canal stenosis and high-signalintensityareas resulting from myelomalacia inspinal cord compression. Short inversion timeinversion-recovery imaging is very sensitive fordetecting most types of soft-tissue and marrowabnormalities and is recommended if the explorationrequires a large field of view, which mayresult in inhomogeneous suppression of fat signalwith T2-weighted sequences. Full-spine andwhole-body MR imaging are also very useful inthe assessment and diagnosis of multifocal lesionsof the skeleton.Bone scintigraphy can be performed whenmultifocal lesions with increased radionuclide uptakeare suspected. However, bone scintigraphy islimited in its capacity to depict detailed surgicalanatomy, particularly compared with CT or MRimaging (3).Decision making before surgical treatmentin patients with spinal tumors requires accuratedelineation of possible vascular involvement. CTangiography and MR angiography are commonlyused to depict the relationship of cervical spinaltumors to the supraaortic trunks. These modalitiesare useful in the evaluation of the artery ofAdamkiewicz in the thoracolumbar region (4) butmay not always replace conventional angiographyin determining the precise relationship betweenthe tumor and the spinal vessels. Moreover, somevascular tumors may require embolization priorto surgery.Evaluation of a Spinal LesionTopographic FeaturesThe common distribution of spinal tumors issummarized in Figure 1. The site of origin of alesion within a vertebra can be difficult to determinein slow-growing and large lesions. Thedistribution of hematopoietic marrow plays animportant role in the distribution of metastaticdisease and hematologic malignancies in the vertebralbodies. Some tumors have a distinct predilectionfor the ends of the spinal column. Chordomais the most common primary distal tumorof the upper cervical spine. It should be differentiatedfrom pseudotumoral lesions of the foramenmagnum such as calcium pyrophosphate dihydratedeposits, synovial pannus, and craniovertebraljunction tuberculosis. Chordomas that developfrom remnants of the primitive notochordTeachingPoint

1022 July-August 2008 RG ■ Volume 28 • Number 4TeachingPointare also frequently found in the sacrococcygealregion. Giant cell tumors commonly involve thesacrum. The sacrum, as a site of hematopoieticor red marrow in the adult, is also a common siteof metastatic disease as well as of hematologicmalignancies including plasmocytoma, myeloma,lymphoma, and Ewing sarcoma.Type of MatrixAs in the peripheral skeleton, the type of tumormatrix can help the radiologist diagnose bone- orcartilage-forming tumors and fibrous dysplasia.Osteoblastic tumors can display amorphousossifications at radiography or CT. The matrixmost often appears amorphous or cloudlike becauseit is less dense than normal bone and lacksan organized trabecular pattern. The amount anddegree of matrix mineralization is widely variable;thus, the radiographic appearance of osteoblastictumors may range from densely blastic to nearlycompletely lytic. Dense osteoblastic lesions displaya low T1-T2 signal intensity pattern at MRimaging. The differential diagnosis of osteoblastictumors includes osteoblastic metastasis, boneisland, lymphoma, and osteosarcoma. Osteoblastictumors should be differentiated from reactivebone sclerosis adjacent to osteoid osteoma andosteoblastoma.Cartilage-forming tumors typically exhibitpunctate commalike or annular calcifications atradiography and CT. These calcifications appearas low-signal-intensity foci at MR imaging. Cartilagelobulations display high signal intensity onT2- and short inversion time inversion-recovery–weighted images owing to the high water contentof the hyaline cartilage. A pattern of enhancingrings and arcs is seen in cartilaginous tumors onpostcontrast images. The differential diagnosisof cartilage-forming tumors includes osteochondroma,chondroblastoma and chondrosarcoma,ABC, and chordoma.Fibrous tissue is nonspecific, with low to intermediatesignal intensity on T1-weighted imagesand variable signal intensity on T2-weighted images.Fibrous dysplasia is easily diagnosed withCT, manifesting as ground-glass attenuation.Other Differential FeaturesFluid-fluid levels were initially described at CT.MR imaging is now the most sensitive methodfor detecting fluid-fluid levels and may also helpdifferentiate liquid from hemorrhage. The imagingfinding of prominent fluid-filled hemorrhagicspaces in a vertebral lesion is suggestive of ABCbut has also been described in telangiectatic osteosarcoma(5,6). Moreover, the high prevalenceof a secondary ABC should indicate the possibilityof finding fluid-fluid levels in a coexisting tumor.Vertical striations or a “honeycomb” pattern arehighly suggestive of vertebral hemangioma. Fatcontent within lesions can be found in vertebralhemangioma, fibrous dysplasia, Paget disease,and Schmörl node.Margins and LimitsBenign tumors usually exhibit geographic bonedestruction and sclerotic margins without softtissueextension (except ABC, aggressive hemangioma,and eosinophilic granuloma). Conversely,malignant tumors usually exhibit poorly definedmargins, permeative bone destruction, and asoft-tissue mass. Marrow and, more particularly,soft-tissue edema, is frequently seen adjacent toprimary bone tumors.Locoregional ExtensionCervical spinal tumors require CT angiographicor MR angiographic evaluation to depict theirrelationship to the supraaortic trunks. Thoracicspinal tumors require accurate delineation of therelationship of the lesion to the pleura, mediastinum,and ribs. In the lumbar region, spinal tumorsmay involve the retroperitoneum. For sacraltumors, it is important to delineate lesion extensionto the sacroiliac joints and pelvis.Bone-forming TumorsBone IslandBone islands, or enostoses, are asymptomatic lesionsthat are discovered incidentally in patientsof all ages. They are not true neoplasms andrepresent dense compact bone within spongiosa(developmental abnormality) (Fig 2). Radiographyand CT demonstrate round osteoblasticlesions with “brush border” at their periphery(Fig 3). Enostoses have low signal intensity at T1-and T2-weighted MR imaging. They may showactivity at bone scintigraphy in less than 10% ofcases, and most lesions remain stable. Enostosesvary in size, and some giant enostoses have beenreported in the literature. The primary alternativein the differential diagnosis is osteoblasticmetastasis.Osteoid OsteomaOsteoid osteoma is a benign osteoblastic lesioncharacterized by a nidus of osteoid tissue or evenmineralized immature bone, often surroundedby sclerotic reactive bone. At histologic analysis,

RG ■ Volume 28 • Number 4 Rodallec et al 1023Figure 2. Bone island. Photomicrograph (originalmagnification, ×4; hematoxylin-eosin [H-E] stain)shows a well-delineated area of compact mature lamellarbone similar to cortical bone (C) with peripheralbony spiculations merging with surrounding bone trabeculae(T).Figure 3. Enostosis of the sacrum in a 70-year-oldman with a history of prostate cancer. Coronal reformattedCT image shows a densely sclerotic lesion withradiating spiculations just beneath the cortex. Note thesimilarity of these findings to those in Figure 2.Figure 4. Osteoid osteoma of the lamina at the T8 level in a 34-year-old man with painful scoliosis. (a) CTscan shows the nidus (arrowhead) with a small area of calcification and no perinidal sclerosis. (b) Photomicrograph(original magnification, ×4; H-E stain) reveals a well-delineated nodular bone-forming tumor (*).the nidus is formed by interlacing trabeculae ofosteoid or woven bone with a highly vascularizedstroma. The nidus is less than 1.5 cm in diameterby definition, with larger lesions being called osteoblastomas.The majority of osteoid osteomasoccur in the 2nd and 3rd decades of life, witha male predilection of 2–3:1. The majority ofspinal osteoid osteomas are located in the neuralarch. The lumbar spine is most commonlyaffected, followed by the cervical, thoracic, andsacral segments. Patients with spinal osteoid osteomaclassically present with painful scoliosis.Aspirin usually provides pain relief. The naturalhistory of osteoid osteoma is not fully understood,however, and spontaneous resolution hasbeen reported.At radiography, the complex anatomy of thespine makes the detection and localization of aradiolucent nidus obscured by reactive sclerosismuch more difficult than that of a nidus locatedin a long bone. Bone scintigraphy is almost invariablypositive and has been advocated for localizingthe vertebral level in patients with clinicallysuspected osteoid osteoma. Subsequent targetedCT is generally regarded as the preferred crosssectionaltechnique for the demonstration andprecise localization of the nidus. Osteoid osteomacharacteristically manifests as a low-attenuationnidus with central mineralization and varying degreesof perinidal sclerosis (Fig 4). The nidus ofosteoid osteoma can have a very heterogeneous,variable appearance at MR imaging, makingdetection and characterization difficult. Mosttumors have low to intermediate signal intensityTeachingPoint

1024 July-August 2008 RG ■ Volume 28 • Number 4Figure 5. Osteoblastomaofthe sacrum in a37-year-old manwith sacral pain.CT scan showsa hypoattenuatingarea withcentral calcificationsand minimalsurroundingsclerosis.Figure 7. Osteoblastoma of theL2 posterior arch in a 15-year-oldgirl with painful scoliosis. (a) CTscan shows diffuse osteoid matrix.(b) Sagittal contrast-enhanced fatsaturatedT1-weighted MR imageshows marked enhancement of thelesion (*) and severe inflammationof the surrounding soft tissue involvingthe adjacent vertebral levels(arrowheads) and the posterior archof L1 (arrow) (“flare phenomenon”).on T1-weighted images and variable signal intensityon T2-weighted images, possibly dependingon the vascularity of the tumor and the presenceof calcification (7,8). Dynamic gadolinium-enhancedMR imaging can depict osteoid osteomaswith greater conspicuity than can nonenhancedMR imaging, and with a conspicuity equal to orgreater than that of thin-section CT (2). MR imagingis sensitive in detecting nonspecific changesin the bone marrow and soft tissues, which mayhave a misleading aggressive appearance (7–9).Edema in the pedicle and lamina extending anteriorlyto involve one- to two-thirds of the posterolateralvertebral body with sparing of the intervertebraldisk space should raise suspicion for thediagnosis (10). It is also possible to see edema inthe neural arch at a level adjacent to that whichharbors the nidus.The role of imaging in osteoid osteoma is tohelp identify and accurately localize the tumorprior to surgical or percutaneous treatment (excision,laser treatment, or thermocoagulation).OsteoblastomaThe histologic similarities between osteoid osteomaand osteoblastoma are striking, but theirclinical manifestations and natural histories differ(11). Osteoblastoma causes dull, localized painor is asymptomatic (12). It tends toward progressionand may be locally aggressive, whereasosteoid osteoma tends toward regression (11).Osteoblastoma accounts for 1% of all primarybone tumors, with a male-female ratio of 2:1.Between 32% and 46% of osteoblastomas involvethe spine (13). Ninety percent of osteoblasto-

RG ■ Volume 28 • Number 4 Rodallec et al 1025Figure 6. Aggressive osteoblastoma of the L5 vertebral body in a 34-year-old woman with low back painand neurologic symptoms. (a) CT scan shows a destructive expansile lesion with osteoid matrix extendinginto the spinal canal. (b) Axial T2-weighted MR image shows a mass with low signal intensity. (c) Axial contrast-enhancedfat-saturated T1-weighted MR image shows marked enhancement of the lesion. (d) Photomicrograph(original magnification, ×40; H-E stain) reveals a bone-forming tumor with irregular anastomosingtrabeculae (T) lined by regular osteoblasts and osteoclasts (arrowheads) and with rich vascularity (*).mas manifest in the 2nd and 3rd decades oflife. Osteoblastomas originate in the neural archand often extend into the vertebral body. Spinalosteoblastomas appear with more or less equalfrequency in the cervical, thoracic, and lumbarsegments.At bone scintigraphy, osteoblastoma demonstratesmarked radionuclide uptake. Reactivesclerosis adjacent to the lesion is common at conventionalradiography. The radiologic features ofosteoblastoma are a lesion diameter greater than2 cm, osseous expansion, soft-tissue components,and multifocal matrix mineralization (Fig 5) (14).Tumors that are mainly lytic at CT with littleevidence of matrix mineralization are hypointenseat T1-weighted MR imaging and hyperintenseat T2-weighted imaging (15). Lesions showinglittle matrix mineralization at CT but diffuseosteoid production at histologic analysis havelow signal intensity at T2-weighted MR imaging(Fig 6) (16). Depending on the degree of tumormatrix mineralization, T2-weighted imaging mayshows areas of mixed low and high signal intensity,or the tumor may be mainly of low signalintensity (17). All tumors enhance following theinjection of gadolinium-based contrast material,as would be expected given the vascular nature ofthe lesion. Soft-tissue invasion with cortical destructionmust be differentiated from the severeinflammatory response involving several adjacentbones and soft tissue (Fig 7). The so-called flarephenomenon can cause marked overestimation oflesion size and lead to sampling error (18). Thevariable appearance of the tumor and the adjacent

1026 July-August 2008 RG ■ Volume 28 • Number 4Figure 8. Osteoblastic osteosarcoma of the sacrum in a 20-year-old man with sacral pain, neurologic symptoms,and a palpable mass. (a) CT scan shows permeative bone destruction and osteoid matrix. (b) Axial T2-weighted MR image shows a slightly hypointense lesion with cystic foci (arrowheads). (c) Axial contrast-enhancedfat-saturated T1-weighted MR image shows enhancement of the lesion with cystic foci (arrowheads).(d) Photomicrograph (original magnification, ×40; H-E stain) reveals a high-grade osteoblastic osteosarcomawith a thin net of immature osteoid matrix (arrowheads) interwoven between neoplastic osteoblasts.reactive bone and soft tissue suggest that MRimaging is of limited value in the characterizationand local staging of this lesion (16).Treatment of spinal osteoblastoma consists ofcurettage with bone grafting. Preoperative embolizationmay be useful. The recurrence rate is10%–15%.OsteosarcomaOnly 4% of all osteosarcomas involve the spine(5). Peak prevalence occurs during the 4th decadeof life. Radiation therapy and Paget diseaseare usually implicated in cases of secondaryosteosarcoma in elderly patients. The thoracicand lumbar segments are involved with equal frequency,followed by the sacrum and the cervicalcolumn (5). In 79% of cases, the tumor arises inthe posterior elements with partial vertebral bodyinvolvement (5). Involvement of two vertebrallevels is seen in 17% of cases (5). Patients maypresent with pain, signs of neurologic compression,or a palpable mass.Conventional osteosarcoma is a high-grademalignant osteoblastic lesion with varyingamounts of osteoid production, cartilage, or fibroustissue. In 80% of cases, CT demonstratesmatrix mineralization (Fig 8). Rarely, tumorswith marked mineralization originating in thevertebral body may manifest as an “ivory vertebra”(sclerosing osteoblastic osteosarcoma). A

RG ■ Volume 28 • Number 4 Rodallec et al 1027Figure 9. Osteochondroma of the cervical spine in a 30-year-old man with cervicobrachialneuralgia. (a) Sagittal reformatted CT image shows cortical continuity of the osteochondromawith the C6 posterior arch. (b) Photomicrograph (original magnification, ×2;H-E stain) reveals a regular cartilaginous cap (*) undergoing enchondral ossification (arrowhead)leading to medullary bone (m).purely lytic pattern is also seen in various subtypessuch as telangiectatic osteosarcoma (predominantcystic architecture simulating ABC).MR imaging signal intensity characteristics areusually nonspecific. Fluid-fluid levels have beendescribed in association with telangiectatic osteosarcoma(5,6,19). As opposed to ABCs, telangiectaticosteosarcomas with prominent fluidfilledhemorrhagic spaces are characterized bythick, solid nodular tissue surrounding the cysticspaces, matrix mineralization, and a more aggressivegrowth pattern (6).Patients with osteosarcoma of the spine shouldbe treated with a combination of chemotherapyand at least marginal excision (assuming the tumorsare surgically accessible) (20). Postoperativeradiation therapy may be of benefit in selectedpatients (6).Cartilage-forming TumorsOsteochondromaOsteochondroma represents the most commonbone tumor and is a developmental lesion ratherthan a true neoplasm (21). This lesion is causedby the separation of a fragment of growth platecartilage, which grows as a result of progressiveenchondral ossification, leading to a subperiostealosseous excrescence with a cartilagecap that projects from the bone surface (21).Osteochondromas enlarge as a result of growthat the cartilage cap, identical to a normal physealplate. Enchondral ossification leads to medullarybone with a fatty or hematopoietic mar-row. After skeletal maturity, osteochondromasusually exhibit no further growth (21). Mostosteochondromas are solitary and sporadic lesions,although some are multiple, usually withan autosomal dominant inheritance. Althoughonly 1.3%–4.1% of solitary osteochondromasoriginate in the spine, approximately 9% of patientswith multiple osteochondromas have spinallesions (22). Solitary lesions affect males morefrequently than females (1.9:1 ratio), and theaverage age at diagnosis is 33 years (23). Osteochondromascan arise from any part of the vertebralcolumn, but the cervical spine is commonlyinvolved, with a predilection for the atlantoaxialarea, followed by the thoracic spine and the lumbarspine (22–24). In cases of multiple exostoses,the thoracolumbar spine is more commonly involved.Most spinal lesions occur near the tip ofspinous or transverse processes. They can alsodevelop in the vertebral body, a pedicle, or, morerarely, the articular facet (23). Radiation-inducedosteochondromas occur within or at the peripheryof the radiation field and are usually solitary. Theprevalence following irradiation for childhood malignancyis approximately 12%.Because of overlapping of osseous structuresof the spine, conventional radiography is ofteninsufficient (23). CT is the modality of choice fordemonstrating the diagnostic appearance of marrowand cortical continuity with the underlyingvertebra (Fig 9) (21,23). At MR imaging, the lesionmanifests with a peripheral rim of low signal

1028 July-August 2008 RG ■ Volume 28 • Number 4Figure 10. Chondroblastoma of L3 in a 23-year-old woman with a 6-month history ofpainful lumbar scoliosis. (a) Sagittal reformatted CT image reveals a lytic lesion of the L3vertebral body with sclerotic margins. The lesion involves the right pedicle and articularprocess and extends into the adjacent foramina. (b) On a sagittal T2-weighted MR image,the lesion (arrowheads) appears isointense relative to the normal vertebral bodies and is difficultto visualize. (c) Axial contrast-enhanced fat-saturated T1-weighted MR image showsmarked enhancement of the lesion. (d) Photomicrograph (original magnification, ×40; H-Estain) reveals sheets of uniform chondroblasts with abundant chondroid matrix (*) andsome osteoclast type giant cells (arrowhead).intensity corresponding to the cortical bone anda central area of fat signal intensity correspondingto the central cancellous bone. A thin cartilaginouscap may be present, especially in children (25,26).With age, cartilage tends to thin and disappears atnumerous points on the surface of an osteochondroma(23). However, a thick (>1-cm) cartilaginouscap in an adult patient should raise suspicionfor an exostotic chondrosarcoma (26). Histologicdiagnosis of malignant transformation of osteochondromais mainly based on architectural features,since many tumors show little atypia.Given the difficulty of diagnosing these spinallesions, the difficulty of clinical and radiologicfollow-up, and the risk of malignant transformation,systematic surgical resection is warrantedin all cases of diagnosed spinal osteochondroma(23,27).ChondroblastomaChondroblastoma is a benign cartilaginous tumorwith a predilection for the growing skeleton(28). It is composed of sheets of chondroblastsadmixed with reactive giant cells and variableamounts of chondroid matrix. “Chicken wire”calcification of the matrix is highly typical ofchondroblastoma. Only 1.4% of all chondroblastomasoriginate in a vertebra (29). Most patientspresent during the 3rd decade of life (28–30).The tumor involves the vertebral body and posteriorelements. Back pain is the most commonsymptom (28,30). However, neurologic symptomsmay occur when the spinal canal or foraminaare invaded.The tumor shows aggressive features at imaging,with bone destruction and a soft-tissue massbut no surrounding bone edema (28,29). In othercases, CT may demonstrate a geographic lesionwith sclerotic borders (Fig 10) (30). Most lesionshave hypointense areas on T2-weighted MR images.Low signal intensity on T2-weighted imagesis associated with immature chondroid matrix,hypercellularity, calcifications, and hemosiderinat histologic analysis (31).

RG ■ Volume 28 • Number 4 Rodallec et al 1029Figure 11. Chondrosarcoma of the L4 vertebral body in a 41-year-old man with low back pain. (a) CTscan shows a large mass arising from the vertebral body with cortical disruption and ring and arc calcifications.(b) Axial T2-weighted MR image shows a high-signal-intensity lobulated mass with linear striations. (c) Photomicrograph(original magnification, ×4; H-E stain) shows a well-differentiated cartilaginous tumor (*) withinfiltration of the medullary bone and resorption of a preexistent bone trabecula (arrowhead).Treatment options for this benign tumor includelocal curettage or resection. Because of thehigh rate of local recurrence, total vertebrectomyis the most commonly used technique (30).ChondrosarcomaChondrosarcoma is the second most commonnonlymphoproliferative primary malignant tumorof the spine in adults (32). Peak prevalence occursbetween 30 and 70 years of age (33). Menare affected two to four times more frequentlythan women (32). The thoracic and lumbar spineare most frequently affected, with the sacrumbeing affected only rarely (32,33). Chondrosarcomaoriginates in the vertebral body (15% ofcases), posterior element (40%), or both (45%)at presentation (14). The clinical course of primarychondrosarcoma originating in the spine isusually long because most tumors are low-gradelesions (14,33).Chondrosarcomas of the spine usually manifestas a large, calcified mass with bone destruction(14,33,34). True ossification may also bepresent, which sometimes corresponds to residualosteochondroma in cases of secondary chondrosarcoma(26). Chondroid matrix mineralizationis better demonstrated with CT. Calcified matrixis detected as areas of signal void at MR imaging.The nonmineralized portion of the tumor haslow attenuation on CT scans, low to intermediatesignal intensity on T1-weighted MR images,and very high signal intensity on T2-weightedimages due to the high water content of hyalinecartilage (Fig 11). An enhancement pattern ofrings and arcs at gadolinium-enhanced MR imagingreflects the lobulated growth pattern ofthese cartilaginous tumors. Extension throughthe intervertebral disk has been reported in 35%of cases (35).Chondrosarcoma tends to recur if inadequatelymanaged. En bloc resection provides thebest chance of survival and the lowest rate of localrecurrence (33).

1030 July-August 2008 RG ■ Volume 28 • Number 4Hematopoietic, Reticuloendothelial,and Lymphatic TumorsEosinophilic GranulomaLangerhans cell histiocytosis, previously termedhistiocytosis X, includes conditions that rangefrom the usually solitary and curable eosinophilicgranuloma, to the disseminated process thatproduces Schüller-Christian syndrome, to thedisseminated and rapidly fatal variety known asLetterer-Siwe disease. These three seemingly dissimilarconditions are united by common pathologicfeatures. At histologic analysis, diagnosis ofLangerhans cell histiocytosis is made on the basisof identification of Langerhans cells variably admixedwith inflammatory cells, eosinophils, lymphocytes,neutrophils, and plasma cells. Langerhanscell histiocytosis is a rare condition (onenew case per 2,000,000 persons per year) (36). Itusually occurs in children, with a peak prevalencebetween 5 and 10 years of age. Eighty percent ofcases occur before the age of 30 years. In multifocalinvolvement (10%–20% of cases), osseous lesionsappear simultaneously or within 1–2 years.Vertebral involvement is seen in only 7.8%–25%of cases of Langerhans cell histiocytosis (36).Patients with spinal lesions usually have pain,which subsides rapidly after bed rest. Althoughalmost all vertebral lesions involve collapse of thevertebral body, neurologic complications are rareand usually mild. Some patients may present withmild hyperpyrexia, mild elevation of the erythrocytesedimentation rate, slight eosinophilia, andleukocytosis.The radiographic characteristics of a typicalspinal lesion consist of complete or incompletecollapse of the vertebral body; absence of an osteolyticarea; preservation of pedicles, posteriorelements, and adjacent disk spaces; absence ofadjacent paravertebral soft-tissue shadow; andincreased opacity in the collapsed body (Fig 12)(36). In patients with typical vertebral lesionsbut no suspected malignancy, close observationwith clinical and radiologic examination mightbe more appropriate than vertebral biopsy. Reconstitutionof the vertebral height usually occurs.Most of the remaining normal tissue ofthe collapsed vertebral body is the apophysealplate, which may be damaged during biopsy, thusprecluding reconstitution of the vertebral height(36).Figure 12. Eosinophilic granulomain a 12-year-old boy. Radiograph showsincreased opacity in an incompletely collapsedvertebral body (arrowhead).Treatment of Langerhans cell histiocytosisis still controversial. Patients with a typical lesionwithout complications can be treated withconservative measures. In patients with multifocaldisorders, biopsy of extraspinal lesions isrecommended and chemotherapy is routinelyperformed.PlasmocytomaPlasmocytoma represents focal proliferation ofmalignant plasma cells without diffuse bone marrowinvolvement. These lesions are considered torepresent the early stages of multiple myeloma.Solitary plasmocytoma is an uncommon tumorthat occurs in 3%–7% of patients with plasmacell neoplasms. Seventy percent of patients areover 60 years old (26). The vertebral body isthe most common site of involvement by plasmocytomadue to its rich red marrow content,but the tumor frequently extends to the pedicles(26,37,38). Plasmocytoma usually manifests witha single collapsed vertebra (26,37). A monoclonalseric immunoglobulin is present at a low sericlevel in 40% of cases.In two-thirds of cases, the radiographic appearanceis characteristic, with a mixed, predominantlylytic pattern (26). The tumor preferentiallyreplaces the cancellous bone, whereas the corticalbone is partly preserved or even sclerotic, resultingin a hollow vertebral body or pedicle (26).The cortical thickening in the arrangement ofplasmocytoma appears to be unique to this tumorand results in a “minibrain” appearance onaxial images (Fig 13) (38). In one-third of cases,

RG ■ Volume 28 • Number 4 Rodallec et al 1031Figure 13. Plasmocytoma of C6 in a 36-year-oldman with cervical spinal pain and neurologic symptoms.(a) Lateral radiograph shows a multicysticappearinglesion (arrowhead) involving the vertebralbody and the neural arch at C6. (b) CT scan showsthe minibrain sign created by a lytic vertebral lesionwith cortical preservation. (c) Axial contrast-enhancedfat-saturated T1-weighted MR image showshomogeneous enhancement of the lesion with epiduralextension and spinal cord compression.the radiographic appearance is less characteristic,with a multicystic “soap bubble” appearance simulatinga hemangioma, or perhaps a purely lyticappearance (26). Solitary sclerotic plasmocytomais extremely rare and can be found in associationwith polyneuropathy (39). Like many expansiletumors involving the axial skeleton, plasmocytomahas low signal intensity on T1-weighted MRimages, high signal intensity on T2-weighted images,and homogeneous marked enhancement onpostcontrast T1-weighted images (26,38). Focalendplate fractures are well described in patientswith plasmocytoma (37). Involvement of the intervertebraldisk and adjacent vertebrae can beused to help differentiate plasmocytoma frommetastasis (37).Treatment is based on complete surgical excisionand radiation therapy, with a theoreticchance of cure following early diagnosis. Radiologicsurveillance helps in evaluating treatmentefficiency, local recurrences, metastases, or transformationinto multiple myeloma.LymphomaPrimary lymphoma of bone is a rare extranodalmanifestation of non-Hodgkin lymphoma, accountingfor only about 1%–3% of all lymphomas.Primary bone lymphomas are mainly diffuselarge B-cell lymphomas. Peak prevalence occursin the 5th–7th decades, with a strong male

1032 July-August 2008 RG ■ Volume 28 • Number 4predilection (up to an 8:1 male-female ratio)(28). Spinal involvement in lymphomas resultsmuch more frequently from late metastatic disseminationof Hodgkin disease and non-Hodgkinlymphoma. Spinal involvement may manifest asparaspinal, vertebral, and epidural involvement,either in isolation or in combination (Fig 14)(26). Vertebral involvement results more frequentlyfrom hematogenous spread than fromosseous invasion from adjacent lymph nodes.Vertebral lesions may have a sclerotic, lytic,or mixed appearance. The sclerotic (ivory vertebra)and mixed patterns are more common inHodgkin disease. The appearance of vertebrallymphoma at CT and MR imaging is usuallynonspecific. Bone scintigraphy shows increasedradionuclide uptake in nearly all patients. Nevertheless,a focus of bone marrow replacementand a surrounding soft-tissue mass withoutlarge areas of cortical bone destruction suggestlymphoma (40). Lymphoma is caused by tumorspread from the medullary cavity along the smallvascular channels that run through the cortex. Itcan be seen with other small round cell tumorssuch as Ewing sarcoma. Contiguous vertebral involvementhas also been reported (40). Pathologicstudies of bone biopsy specimens can be difficultdue to crush artifacts, and sometimes largebiopsies are required.A combination of chemotherapy and involvedfieldradiation therapy prolongs event-freesurvival.Ewing SarcomaAlthough the vertebral column is frequently involvedin preterminal metastatic Ewing sarcoma,primary vertebral Ewing sarcoma is quite rare,with a reported prevalence of 3.5%–15% (41).Ewing sarcoma is an undifferentiated high-gradeproliferation of uniform small round cells. Necrosisis common. Primary vertebral Ewing sarcomais usually seen in the 2nd decade of life (meanage, 19.3 years), with a slight male predilection(62% vs 38% of cases) (41). The sacrum is themost frequently involved site (55.2% of cases),followed by the lumbar spine (25%). The cervicalspine is the least frequently affected site (3.2% ofcases). In the nonsacral spine, the majority (60%)of lesions originate in the posterior elementswith extension into the vertebral body. The alais the most frequently affected sacral site (69%of cases). More than one segment is involved in8% of cases (41). The disk spaces are usually preserved(42).Figure 14. B-cell lymphoma in an 80-year-oldwoman with low back pain and cauda equina syndrome.(a) Sagittal T2-weighted MR image shows alow-signal-intensity spinal lesion spreading over multiplelevels (L4–S3) and extending into the epiduraland prevertebral spaces, but without extension throughthe intervertebral disk. (b) Sagittal contrast-enhancedfat-saturated T1-weighted MR image shows heterogeneousenhancement of the lesion.Lesions may be lytic, sclerotic, or mixed withassociated vertebral compression. Nearly all tumors(93%) are lytic and morphologically aggressive.A purely sclerotic pattern is rare and mightcorrespond to necrotic and reactive bone formation.Other unusual imaging findings includevertebra plana, ivory vertebra, and pseudohemangioma(41,42). Invasion of the spinal canal iscommon (91% of cases), often with a large mass.The paraspinal component is often larger thanthe intraosseous lesion (42).Patients receive a combination of chemotherapyand local radiation therapy. Patients with evidenceof instability and neurologic compromisemay still require surgical decompression andstabilization.Vertebral HemangiomaVertebral hemangioma is considered to be alesion of bone—usually of dysembryogeneticorigin—or a hamartomatous lesion. It is composedof thin-walled vessels lined by flat, blandendothelial cells infiltrating the medullary cavitybetween bone trabeculae. Spinal hemangiomasare common and frequently multiple. The prevalenceof hemangiomas seems to increase with ageand is greatest after middle age, with a slight femalepredilection. Most hemangiomas are seen in

RG ■ Volume 28 • Number 4 Rodallec et al 1033Figures 15, 16. (15) Hemangioma of the T9 vertebral body in an 81-year-old woman with multiple osteoporoticcompression fractures (T10–T12). (a) Sagittal T1-weighted MR image shows fat signal intensity throughout theT9 vertebral body (arrowhead), with linear low-signal-intensity striations due to thickened trabeculae. (b) Axial T2-weighted MR image shows a well-circumscribed fatty lesion with coarse vertical trabeculae (polka dots). (16) Aggressivehemangioma in a 53-year-old man. Axial contrast-enhanced fat-saturated T1-weighted MR image shows anavidly enhanced lesion with coarse vertical trabeculae and extraosseous extension into the epidural space.the thoracic and lumbar spine. They are usuallyconfined to the vertebral body, although they mayoccasionally extend into the posterior elements.Most spinal hemangiomas are asymptomatic. Occasionally,vertebral hemangiomas may increasein size and compress the spinal cord and nerveroots. Compressive vertebral hemangiomas canoccur in patients of any age, with a peak prevalencein young adults, and preferentially occur inthe thoracic spine (43).Hemangiomas in vertebrae cause rarefactionwith exaggerated vertical striations or a coarsehoneycomb appearance. CT shows the pattern asmultiple dots (polka-dot appearance) representinga cross-section of reinforced trabeculae. Atscintigraphy, the appearance of osseous hemangiomasranges from photopenia to a moderateincrease in radiotracer uptake. The histopathologicfeatures of hemangiomas—high vascularity,interstitial edema, and interspersed fat—dictatethe MR imaging appearance. The presence ofhigh signal intensity on T1- and T2-weighted MRimages is related to the amount of adipocytes orvessels and interstitial edema, respectively (44).Thick, low-signal-intensity vertical struts maybe seen within hemangiomas. Fatty vertebral hemangiomasmay represent inactive forms of thislesion (Fig 15), whereas low signal intensity atMR imaging may indicate a more active lesionwith the potential to compress the spinal cord(45). The radiographic and CT appearances ofcompressive vertebral hemangiomas can be misleading,with irregular trabeculae and lytic areas;poorly defined, expanded cortex; and soft-tissueexpansion (43,46). Mottled high signal intensityon T1-weighted MR images can be expected inonly about 50% of compressive vertebral hemangiomas(Fig 16), and signal voids are the mostuseful additional MR imaging sign in lesions thatare hypointense on T1-weighted images (46).The differential diagnosis of compressive hemangiomaswith a coarse reticular pattern and extraduralextension includes rare hemangioblastoma,lymphangioma, and Ewing sarcoma (42,47,48).Transarterial embolization is an effective treatmentfor painful intraosseous hemangioma andis useful in reducing intraoperative blood lossbefore decompressive surgery (49). Rapid tumorgrowth with spinal cord compression should bemanaged surgically (50). Highly vascular (cavernoustype) hemangiomas may sometimes producea prominent neurologic deficit despite scant evidenceof spinal cord compression. The neurologicdeficit in these cases is believed to be attributableto blood flow disturbances in the spinal cord(50). Radiation therapy can yield satisfactory results,with the obliteration of vessels and tumorshrinkage (50).ChordomaChordoma is a rare malignant neoplasm arisingfrom the remnants of the primitive notochord.

1034 July-August 2008 RG ■ Volume 28 • Number 4At gross examination, chordomas form a soft,white, multilobulated mass delineated by a fibrouspseudocapsule (14,51). The characteristicphysaliphorous cells are the hallmark of chordoma(14,51). Chondroid chordoma exhibitscartilaginous differentiation, but this variation inhistologic appearance does not affect the biologicbehavior of the tumor. Fluid and gelatinous mucoidsubstance, recent and old hemorrhage, necroticareas, and, in some cases, calcifications andsequestered bone fragments are found within thetumor (51). Next to lymphoproliferative tumors,chordomas are the most common primary malignantneoplasm of the spine in adults (14,52).Chordomas generally occur in late middle age,with a peak prevalence in the 5th–6th decades(51). Spinal chordomas have a 2:1 male-femaleratio (51). Chordomas most commonly arise inthe sacrococcygeal region (50% of cases), followedby the spheno-occipital region (35%)and the vertebral bodies (15%). Sacrococcygealtumors usually start in the lower sacrum and coccyx(26). Spinal chordomas arise more frequentlyin the cervical spine than in the thoracic andlumbar regions (51,53). The most common siteof involvement in the mobile spine is the vertebralbody with sparing of the posterior elements(51,53,54). Clinical manifestation is often subtlebecause chordomas are slow-growing lesions(14).The most suggestive manifestation is a destructivelesion of a vertebral body associatedwith a soft-tissue mass with a “collar button”or “mushroom” appearance and a “dumbbell”shape, spanning several segments and sparingthe disks (51). Areas of amorphous calcificationsare noted in 40% of chordomas of the mobilespine and in up to 90% of sacrococcygeal lesions(Fig 17) (14). Most chordomas are iso- or hypointenserelative to muscle on T1-weighted MRimages. The focal areas of hemorrhage and highprotein content of the myxoid and mucinous collectionsthat may be seen in chordomas accountfor the high signal intensity on T1-weighted images(14). On T2-weighted images, most chordomashave a high signal intensity that reflectstheir high water content (Fig 18). The fibroussepta that divide the gelatinous components ofthe tumor are seen as areas of low signal intensityon T2-weighted images. The presence of hemosiderinalso accounts for the low signal intensityseen on T2-weighted images. This MR imagingfeature has been reported in 72% of sacrococcygealchordomas but is rare in spinal chor-Figure 17. Sacrococcygeal chordoma in a76-year-old man. CT scan shows a midline softtissuemass with amorphous calcifications.domas (55). After the injection of gadoliniumbasedcontrast material, most tumors demonstratemoderate heterogeneous enhancement,but ring and arc enhancement and peripheralenhancement have also been described (51).Chordoma is a low-grade and slow-growingtumor but generally has a poor long-term prognosisdespite its low tendency to metastasize.Death is often related to local recurrence. Prognosisdepends on the possibility of margin-free enbloc resection (56). Radiation therapy may alsobe used as an adjunct treatment.Chordoma should be differentiated from giantnotochordal rest, which may also show physaliphorouscells at biopsy. Unlike in chordoma, radiographyand CT fail to demonstrate a distinctlesion in giant notochordal rest, instead showingeither normal bone or a variable degree of sclerosis(57). Bone scintigraphic findings are typicallynormal, whereas MR imaging shows a lesionwith low T1 and high T2 signal intensity and nosoft-tissue involvement. If the lesion is found incidentally,periodic imaging studies help ensurethat the lesion is not progressive with evidence ofbone destruction, the occurrence of which wouldindicate that the lesion is malignant (57).Aneurysmal Bone CystABC is a benign bone lesion of unknown origin.It is a relatively rare lesion that represents1.4%–2.3% of primary bone tumors. The spineis involved in 3%–20% of cases (58,59). At histologicanalysis, ABC is typically characterized byblood-filled cystic spaces separated by a spindlecell stroma with osteoclast-like giant cells andosteoid or bone production (60). Mineralizedchondroidlike material is present histologically

RG ■ Volume 28 • Number 4 Rodallec et al 1035Figure 18. Chordoma of the cervical spine in a 50-year-old woman with neurologic symptoms. (a) Sagittalcontrast-enhanced T1-weighted MR image shows a heterogeneously enhanced lesion invading the C5 andC6 vertebral bodies and nearly sparing the C5–C6 intervertebral disk. (b) Sagittal T2-weighted MR imageshows the lesion with high signal intensity and invading the C6 vertebral body and epidural space. Note themushroomlike appearance of the lesion. (c) Photomicrograph (original magnification, ×40; H-E stain) revealssheets of vacuolated cells (the characteristic physaliphorous cells [arrowhead]) within an abundant myxoidbackground (*).in approximately one-third of cases of ABC. Thesolid variant of ABC is a rare lesion, accountingfor 3.4%–7.5% of all conventional ABCs (60).Spindle cell proliferation is the predominant histologiccomponent of the solid variant of ABC,which can be mistaken for other tumors of thespine. The lack of anaplasia in all the tissue componentsstrongly argues against a malignant tumor(60). The three main hypotheses reported inthe literature propose that the lesion is the resultof either the improper repair of a traumatic subperiostealhemorrhage, a vascular disturbance ofthe bone, or hemorrhage into a preexisting lesion(61). In 29%–35% of cases, a preexisting lesioncan be identified. The most common of these isgiant cell tumor, which accounts for 19%–39%of cases in which a preexisting lesion is found(62). Other common precursor lesions includeosteoblastoma, angioma, and chondroblastoma,whereas uncommon precursor lesions includefibrous dysplasia, fibrous histiocytoma, eosinophilicgranuloma, osteosarcoma, and even metastaticcarcinoma (62). ABC usually occurs betweenthe ages of 5 and 20 years but can manifestat any age. There may be a slight female predilection(59). The cervical spine is affected in 22%of cases, the thoracic spine in 34%, the lumbarspine in 31%, and the sacrum in 13% (60). Spinalinvolvement is typically in the posterior elements,although extension into the vertebral bodyis common (75% of cases) (62). Spinal ABC mayextend into the adjacent vertebrae or intervertebraldisk, the ribs, and the paravertebral soft tissue(14,62). The symptomatology varies tremen-dously with the size of the tumor. Most patientshave pain and swelling, and vertebral lesionsfrequently cause signs and symptoms related tocompression of the spinal cord, nerve root, orboth (61).The natural history of ABC has been describedas evolving through four radiologic stages:initial, active, stabilization, and healing (62). Inthe initial phase, the lesion is characterized by awell-defined area of osteolysis. This is followed bya growth phase, in which the lesion has a purelylytic pattern and sometimes ill-defined margins.Later, during the stabilization phase, the characteristicsoap bubble appearance develops as a resultof maturation of the bony shell. CT and MRimaging typically show a well-defined lesion withinternal septation (14,62). Mineralized chondroidlikematerial may be seen at radiographyand CT only when abundant (62). In a series byHudson (63), 35% of ABCs showed fluid-fluidlevels at CT. Hudson emphasized the need toview such scans with a narrow window settingto identify small differences in fluid attenuationand to allow time for the fluid to settle and createfluid levels (63). Fluid-fluid levels within ABCsare indicative of hemorrhage with sedimentationand are better demonstrated with MR imaging.On T1-weighted images, they may have increasedsignal intensity due to methemoglobin in eitherthe dependent or nondependent component(14). Gadolinium-based contrast material injectiondemonstrates smooth enhancement of the

1036 July-August 2008 RG ■ Volume 28 • Number 4Figure 19. ABC of the lumbar spine (L3) in a 34-year-old woman with low back pain. (a) CT scanshows a sharply demarcated and multiloculated lesion with peripheral calcifications and fluid-fluid levelsdue to layering of blood products. (b) Coronal contrast-enhanced T1-weighted MR image shows enhancedsepta between cysts. (c) On a coronal T2-weighted MR image, the signal intensity of cysts varieswith stage of blood degradation. (d) Photomicrograph (original magnification, ×20; H-E stain) revealsreactive bone (R) and classic “blue bone” (B) in the wall of a cyst.internal septa within ABCs (Fig 19). The lesionmargins show a low-signal-intensity rim on MRimages that is thought to be caused by an intact,thickened periosteal membrane (14). Other areasusually show high signal intensity on T2-weightedimages. The presence of a solid component withdiffuse contrast enhancement should raise suspicionfor secondary ABC, although it might be encounteredin the solid variant of ABC (60). Thepredominant bone scintigraphic pattern in ABCis moderate to intense radiotracer accumulationat the periphery of the lesion with little activityat its center (“doughnut sign”), a finding thatis evident in about 64% of cases. However, thisscintigraphic pattern lacks specificity, since it isalso found in giant cell tumor, chondrosarcoma,and telangiectatic osteosarcoma (3).Current treatment recommendations usuallyinvolve preoperative selective arterial embolization,intralesional excision curettage, bone grafting,and fusion of the affected area if instability ispresent (14,26,58,60,61).Giant Cell TumorGiant cell tumor is composed of sheets of stromalovoid mononuclear cells with uniformly distributedosteoblastic giant cells. This tumor occursin skeletally mature patients in the 2nd–4th decadesof life, more frequently in females (64,65).Seven percent of giant cell tumors occur in thespine. The sacrum is affected in 90% of suchcases. The tumor is usually located in the upperFigure 20. Giant cell tumor of the uppersacrum in a 33-year-old woman. Coronal reformattedCT image shows a well-defined lyticlesion of the right upper part of the sacrum withextension through the right sacroiliac joint andabsence of a sclerotic rim.

RG ■ Volume 28 • Number 4 Rodallec et al 1037Figure 21. Giant cell tumor invading the prevertebral space at the C3 level in a 30-year-old man witha history of ABC of C3 that had been treated with curettage, bone grafting, and fusion 4 years earlier.(a) Sagittal reformatted CT image shows a prevertebral soft-tissue mass bulging into the oropharynxand hypopharynx. (b) Sagittal contrast-enhanced T1-weighted MR image shows heterogeneous enhancementof the lesion (arrowheads). (c) Sagittal T2-weighted MR image shows the lesion with lowsignal intensity (arrowheads). (d) Photomicrograph (original magnification, ×40; H-E stain) revealsfocal fibrous changes with hemosiderin deposits (arrowheads). Photomicrograph in inset (original magnification,×100; H-E stain) shows osteoclast type giant cells with numerous nuclei (*) scattered amongregular mononuclear cells.sacrum and frequently lateralized in a sacral wing(26). Extension to the iliac wing through thesacroiliac joint is possible. Above the sacrum, thelumbar, thoracic, and cervical spine (in decreasingorder of frequency) may be affected (64).The tumor usually predominates in the vertebralbody, with frequent involvement of the posteriorarch (64). The tumor is limited to the vertebralbody and pedicles in only 21% of cases (64). Extraosseousinvolvement of the soft tissues is seenin 79% of cases (64). Giant cell tumors of thethoracic spine can sometimes simulate posteriormediastinal neoplasms (66). Intervertebral diskinvasion and extension into an adjacent vertebra ispossible (65).Radiography typically shows a lytic lesion withcortical expansion (26,65). A purely osteolyticpattern is also possible. CT demonstrates absenceof mineralization and the lack of a scleroticrim at the margins of the tumor (Fig 20). Bonescintigraphy shows increased radiotracer uptakein all patients. The tumor usually has low to intermediatesignal intensity on T1-weighted MRimages. Areas of high signal intensity can suggestrelatively recent hemorrhage. More specifically,most giant cell tumors of the spine have low tointermediate signal intensity on T2-weightedimages (67,68). This appearance seems to becaused by hemosiderin deposition and high collagencontent (Fig 21) (67,68). Enhancementof the lesion reflects its vascular supply. Cysticareas, foci of hemorrhage, fluid-fluid levels, and aperipheral low-signal-intensity pseudocapsulemay also be seen (26,67).Giant cell tumors of the spine should becompletely removed; because of their location,however, this usually means excision with an

1038 July-August 2008 RG ■ Volume 28 • Number 4Figure 22. Fibrous dysplasia of the lumbar spine (L4) in a 45-year-old woman with low back pain. (a) CTscan shows a mildly expansile lytic lesion with a sclerotic rim involving the vertebral body and the neural arch.The lesion also demonstrates ground-glass matrix (arrowhead). (b) Photomicrograph (original magnification,×20; H-E stain) reveals curvilinear trabeculae of immature bone (arrowheads) within a hypocellular fibrousstroma.Paget DiseasePaget disease is a chronic metabolic disorder ofabnormal bone remodeling in the adult skeleton.It is rare in patients less than 40 years old. Pagetdisease occurs more frequently in Caucasiansof Northern European descent and is rare inAsians and African-Americans. In the spine, thevertebra is expanded. The typical “picture frame”vertebra shows a coarse and sclerotic peripheraltrabecular pattern and central osteopenia. Otherpatterns of pagetic vertebrae include ivory verteintralesionalmargin (65). Lesions with extensioninto the spinal canal and paraspinous space haveslightly higher recurrence rates (64). Because ofthe risk of sarcomatous transformation, radiationtherapy should be reserved for patients with incompleteexcision or local recurrence (65).Fibrous DysplasiaFibrous dysplasia is a benign fibro-osseous lesioncharacterized by irregularly shaped trabeculae ofwoven bone and a fibrous component composedof cytologically bland spindle cells. It occurs inboth children and adults and has an equal genderdistribution. Vertebral involvement is rare but occursmore frequently with polyostotic disease. Thelesion is frequently asymptomatic, but pain andfractures may be part of the clinical spectrum.Radiography and CT usually show a mildlyexpansile lesion with a “blown-out” cortical shellor a lytic lesion with a sclerotic rim. “Groundglass”matrix is common and characteristic (Fig22). Lesions may also contain islands of cartilage.Fibrous dysplasia has variable MR imagingcharacteristics—typically, intermediate to low signalintensity on T1-weighted images and variablesignal intensity on T2-weighted images (69). Fibrousdysplasia shows a mild to marked increasein radionuclide uptake at bone scintigraphy.Conservative treatment can be undertaken inpatients with minimal symptoms. Fibrous dysplasiararely undergoes sarcomatous transformation.Malignant transformation must be suspectedwhen there is cortical erosion, especially with anassociated soft-tissue mass.Differential Diagnosisof Primary Spinal TumorsMetastatic DiseaseMetastases are the most common vertebraltumors. Osteolytic metastases occur more frequentlythan osteoblastic metastases. Somemetastases have a mixed pattern, with areas ofosteolysis and areas of sclerosis. Typically, metastasesare multiple and of variable size withcortical disruption (osteolytic lesions). Vertebralcompression fracture and epidural tumor arecommon in metastases. Some slow-growing metastasesmay mimic a primary bone tumor withmineralization and sclerotic margins. Osteolyticmetastases are most often caused by carcinomaof the lung, breast, thyroid, kidney, and colon and(in childhood) neuroblastoma. Osteoblastic metastasesare most commonly caused by prostatecarcinoma in elderly men and by breast cancer inwomen. Other osteoblastic metastases are causedby lymphoma, carcinoid tumors, mucinous adenocarcinomaof the gastrointestinal tract, pancreaticadenocarcinoma, bladder carcinoma, neuroblastoma,and (in childhood) medulloblastoma.

RG ■ Volume 28 • Number 4 Rodallec et al 1039bra and isolated posterior arch involvement (70).The pagetic bone marrow contains fatty areaswith a heterogeneous distribution. Bone scintigraphydemonstrates the extent of Paget disease.Sarcomatous transformation of the lesion is rare(

1040 July-August 2008 RG ■ Volume 28 • Number 43. Wang K, Allen L, Fung E, Chan CC, Chan JC,Griffith JF. Bone scintigraphy in common tumorswith osteolytic components. Clin Nucl Med 2005;30(10):655–671.4. Yoshioka K, Niinuma H, Ehara S, Nakajima T, NakamuraM, Kawazoe K. MR angiography and CTangiography of the artery of Adamkiewicz: state ofthe art. RadioGraphics 2006;26(suppl 1):S63–S73.5. Ilaslan H, Sundaram M, Unni KK, Shives TC.Primary vertebral osteosarcoma: imaging findings.Radiology 2004;230(3):697–702.6. Murphey MD, wan Jaovisidha S, Temple HT, GannonFH, Jelinek JS, Malawer MM. Telangiectaticosteosarcoma: radiologic-pathologic comparison.Radiology 2003;229(2):545–553.7. Davies M, Cassar-Pullicino VN, Davies AM, Mc-Call IW, Tyrrell PN. The diagnostic accuracy ofMR imaging in osteoid osteoma. Skeletal Radiol2002;31(10):559–569.8. Assoun J, Richardi G, Railhac JJ, et al. Osteoidosteoma: MR imaging versus CT. Radiology 1994;191(1):217–223.9. Woods ER, Martel W, Mandell SH, Crabbe JP.Reactive soft-tissue mass associated with osteoidosteoma: correlation of MR imaging featureswith pathologic findings. Radiology 1993;186(1):221–225.10. Harish S, Saifuddin A. Imaging features of spinalosteoid osteoma with emphasis on MRI findings.Eur Radiol 2005;15(12):2396–2403.11. Greenspan A. Benign bone-forming lesions:osteoma, osteoid osteoma, and osteoblastoma—clinical, imaging, pathologic, and differential considerations.Skeletal Radiol 1993;22(7):485–500.12. Obenberger J, Seidl Z, Plas J. Osteoblastoma inlumbar vertebral body. Neuroradiology 1999;41(4):279–282.13. Lucas DR, Unni KK, McLeod RA, O’Connor MI,Sim FH. Osteoblastoma: clinicopathologic study of306 cases. Hum Pathol 1994;25(2):117–134.14. Murphey MD, Andrews CL, Flemming DJ, TempleHT, Smith WS, Smirniotopoulos JG. Primarytumors of the spine: radiologic-pathologic correlation.RadioGraphics 1996;16(5):1131–1158.15. Ozkal E, Erongun U, Cakir B, Acar O, Uygun A,Bitik M. CT and MR imaging of vertebral osteoblastoma:a report of two cases. Clin Imaging 1996;20(1):37–41.16. Shaikh MI, Saifuddin A, Pringle J, Natali C, SheraziZ. Spinal osteoblastoma: CT and MR imagingwith pathological correlation. Skeletal Radiol 1999;28(1):33–40.17. Nemoto O, Moser RP Jr, Van Dam BE, Aoki J,Gilkey FW. Osteoblastoma of the spine: a review of75 cases. Spine 1990;15(12):1272–1280.18. Crim JR, Mirra JM, Eckardt JJ, Seeger LL. Widespreadinflammatory response to osteoblastoma:the flare phenomenon. Radiology 1990;177(3):835–836.19. Tsai JC, Dalinka MK, Fallon MD, Zlatkin MB,Kressel HY. Fluid-fluid level: a nonspecific findingin tumors of bone and soft tissue. Radiology 1990;175(3):779–782.20. Ozaki T, Flege S, Liljenqvist U, et al. Osteosarcomaof the spine: experience of the CooperativeOsteosarcoma Study Group. Cancer 2002;94(4):1069–1077.21. Murphey MD, Choi JJ, Kransdorf MJ, FlemmingDJ, Gannon FH. Imaging of osteochondroma:variants and complications with radiologicpathologiccorrelation. RadioGraphics 2000;20(5):1407–1434.22. Albrecht S, Crutchfield JS, SeGall GK. On spinalosteochondromas. J Neurosurg 1992;77(2):247–252.23. Gille O, Pointillart V, Vital JM. Course of spinal solitaryosteochondromas. Spine 2005;30(1):E13–E19.24. Sharma MC, Arora R, Deol PS, Mahapatra AK,Mehta VS, Sarkar C. Osteochondroma of the spine:an enigmatic tumor of the spinal cord—a series of10 cases. J Neurosurg Sci 2002;46(2):66–70.25. Khosla A, Martin DS, Awwad EE. The solitaryintraspinal vertebral osteochondroma: an unusualcause of compressive myelopathy—features andliterature review. Spine 1999;24(1):77–81.26. Laredo JD, el Quessar A, Bossard P, Vuillemin-Bodaghi V. Vertebral tumors and pseudotumors.Radiol Clin North Am 2001;39(1):137–163, vi.27. Hudson TM, Chew FS, Manaster BJ. Scintigraphyof benign exostoses and exostotic chondrosarcomas.AJR Am J Roentgenol 1983;140(3):581–586.28. Motamedi K, Ilaslan H, Seeger LL. Imaging of thelumbar spine neoplasms. Semin Ultrasound CTMR 2004;25(6):474–489.29. Ilaslan H, Sundaram M, Unni KK. Vertebral chondroblastoma.Skeletal Radiol 2003;32(2):66–71.30. Vialle R, Feydy A, Rillardon L, et al. Chondroblastomaof the lumbar spine: report of two casesand review of the literature. J Neurosurg Spine2005;2(5):596–600.31. Jee WH, Park YK, McCauley TR, et al. Chondroblastoma:MR characteristics with pathologiccorrelation. J Comput Assist Tomogr 1999;23(5):721–726.32. Murphey MD, Walker EA, Wilson AJ, KransdorfMJ, Temple HT, Gannon FH. Imaging of primarychondrosarcoma: radiologic-pathologic correlation.RadioGraphics 2003;23(5):1245–1278.33. Boriani S, De Iure F, Bandiera S, et al. Chondrosarcomaof the mobile spine: report on 22 cases.Spine 2000;25(7):804–812.34. Lloret I, Server A, Bjerkehagen B. Primary spinalchondrosarcoma: radiologic findings with pathologiccorrelation. Acta Radiol 2006;47(1):77–84.35. Shives TC, McLeod RA, Unni KK, Schray MF.Chondrosarcoma of the spine. J Bone Joint SurgAm 1989;71(8):1158–1165.36. Yeom JS, Lee CK, Shin HY, Lee CS, Han CS,Chang H. Langerhans’ cell histiocytosis of thespine: analysis of twenty-three cases. Spine 1999;24(16):1740–1749.37. Shah BK, Saifuddin A, Price GJ. Magnetic resonanceimaging of spinal plasmacytoma. Clin Radiol2000;55(6):439–445.38. Major NM, Helms CA, Richardson WJ. The “minibrain”: plasmacytoma in a vertebral body on MRimaging. AJR Am J Roentgenol 2000;175(1):261–263.39. Voss SD, Murphey MD, Hall FM. Solitary osteoscleroticplasmacytoma: association with demyelinatingpolyneuropathy and amyloid deposition.Skeletal Radiol 2001;30(9):527–529.40. Mulligan ME, McRae GA, Murphey MD. Imagingfeatures of primary lymphoma of bone. AJR Am JRoentgenol 1999;173(6):1691–1697.

RG Volume 28 • Volume 4 • July-August 2008 Rodallec et alDiagnostic Imaging of Solitary Tumors of the Spine: What to Doand SayMathieu H. Rodallec, MD, et alRadioGraphics 2008; 28:1019–1041 • Published online 10.1148/rg.284075156 • Content Codes:Page 1020Some tumors have a predilection for specific age groups. In patients under 30 years of age, tumors ofthe spine are fairly uncommon and are generally benign except for Ewing sarcoma and osteosarcoma.In patients over 30 years of age, most tumors are malignant except for vertebral hemangiomas andbone islands. Metastases are the most common lesions.Page 1021Chordoma is the most common primary distal tumor of the upper cervical spine. It should bedifferentiated from pseudotumoral lesions of the foramen magnum such as calcium pyrophosphatedihydrate deposits, synovial pannus, and craniovertebral junction tuberculosis.Page 1022Osteoblastic tumors can display amorphous ossifications at radiography or CT. The matrix mostoften appears amorphous or cloudlike because it is less dense than normal bone and lacks anorganized trabecular pattern. The amount and degree of matrix mineralization is widely variable;thus, the radiographic appearance of osteoblastic tumors may range from densely blastic to nearlycompletely lytic.Pages 1023Bone scintigraphy is almost invariably positive and has been advocated for localizing the vertebrallevel in patients with clinically suspected osteoid osteoma. Subsequent targeted CT is generallyregarded as the preferred cross-sectional technique for the demonstration and precise localization ofthe nidus. Osteoid osteoma characteristically manifests as a low-attenuation nidus with centralmineralization and varying degrees of perinidal sclerosis. The nidus of osteoid osteoma can have avery heterogeneous, variable appearance at MR imaging, making detection and characterizationdifficult.Page 1039MR imaging plays a central role in the work-up of a patient who presents with a spinal tumor,although some benign spinal lesions can display a very aggressive and misleading appearance at MRimaging. Consequently, radiography or even CT should be performed when lesions result in extensivesignal intensity abnormalities at MR imaging.