Vol 39 # 2 June 2007 - Kma.org.kw

172Solid and Papillary Epithelial Neoplasm (SPEN) of the Pancreas in a Pregnant Lady June 2007Fig. 6: CT abdomen with oral and I.V. contrast showing post-operativeinfarcts in the spleenand the patient has since been well.Pathologically, the gross specimen measured 20x 16 x 11 cm. It weighed 1.450 kg. It had a thinfibrous capsule and a hemorrhagic, partly necroticcenter. Microscopically, the tumor had solid, cystic,pseudo-papillary and trabecular pattern of growth.The solid component showed poorly supportedvessels. Areas of myxoid change with thin bloodfilled channels were noted. The tumor cells hadovoid nuclei and granular eosinophilic cytoplasm.At one focus, invasion of the capsule was noted.Findings confirmed the diagnosis of SPEN.DISCUSSIONCystic neoplasms of the pancreas are relativelyuncommon, representing only 10-15% of pancreaticcysts and 1% of pancreatic cancers [4] . SPENs arerare pancreatic tumors with a reported incidence of0.17% to 2.5% among exocrine pancreatic tumors [5] .Pre-operative diagnosis is important, since surgicalresection is curative. They occur in young femaleswith an average age of 24 years [3] . When found inolder females, these tumors are associated with ahigher grade of malignancy [6] .SPENs are large tumors with an averagediameter of 9 to 18 cm [6] and about 58% arise in thetail of the pancreas [1] . On imaging, these tumors canbe solid [3] , but are usually cystic with a well formedcapsule.It is well characterized on ultrasound by areas ofinternal hemorrhage seen as increased internalechoes, along with cystic degeneration, fluid-debrislevels and posterior enhancement due to the cysticcomponent. Peripheral calcification may be present,but is better detected by CT [4,5] . Mural nodules arealso occasionally seen by ultrasound.On computed tomography, the SPEN has a solidperiphery and central cystic degeneration withhemorrhage. The fluid contents hence show densitygreater than water. Peripheral calcification, whenpresent, is best detected by this modality. A welldefinedhypodense capsule is seen, which showsenhancement with contrast. Tumor vascularity ismoderate [2,4,6] .MR has proved to be a valuable modality in theevaluation of SPEN. Because MR imaging issensitive to fluid, it has great potential in theassessment of cystic neoplasms [6,7] . T1 and T2Wimages demonstrate a heterogeneous welldemarcatedmass with areas of low and high signalintensity respectively. This appearance reflects thecomplex nature of the solid, cystic, hemorrhagicand necrotic components [1] . The cyst fluid improvesthe contrast resolution within the mass, delineatingsubtle irregularities of the cyst wall which aid in thed i ff e rential diagnosis between benign and malignantneoplasms, and pseudocysts [7] . It also increases thespecificity by demonstrating the hemorrh a g i ccomponent on T1 weighting due to theparamagnetic component of methemoglobin [6,8] . Thefibrous capsular rim is hypointense on T1 and T2.The capsule and the solid portion of the tumor mayenhance with gadolinium. This mass can be seen todisplace adjacent stru c t u res, as in this study,without invasion [1, 6] .P a t h o l o g i c a l l y, SPEN is a large wellencapsulatedmass. It has a thick fibrous capsulewith mixed cystic, solid and pseudopapillarypattern. The solid areas consist of sheets ofepithelial cells whereas the papillary areas consistof a fibrovascular core lined with cuboidal orcolumnar epithelial cells. Hemorrhage occurs dueto the rupture of the poorly supported vascularnetwork traversing the tumor [1,2,5] .The differential diagnosis would include thegamut of cystic pancreatic neoplasms including thes e rous or microcystic adenomas, mucinous ormacrocystadenomas, cystic non functioning isletcell tumors and intraductal papillary mucinoustumors [1,2,5] . The age of presentation, the site of thetumor within the pancreas (i.e., head, body or tail)and the cross-sectional imaging characteristics ofsize of the tumor, presence or absence ofcalcification and septae and the presence of acapsule would help in the differentiation of theselesions. The main distinguishing features are asfollows:Serous or microcystic cystadenoma or glycogenrich cystadenoma presents in 60 year old females,usually in the region of the head of the pancreas. Ithas thin septae separating multiple cysts 1 mm to 2cm in size which are distributed in a peripherallocation within the tumor giving it a honeycomb ora lace like appearance. Central stellate scars with asunburst pattern of calcification can be seen. MRimaging shows delayed enhancement of the scar oncontrast enhanced images. These are usually benigntumors [2,8,9] .