Pathology of the Head and Neck

120 P.J. Slootweg4Fig. 4.26. Clear cell odontogenic carcinoma is characterised byclear cells forming epithelial nestsFig. 4.27. At higher magnification, clear cell odontogenic carcinomais seen to contain clear cells as well as eosinophilic cellsSwelling of the jaw and pain are most often the presentingsigns. Surgery and postoperative radiotherapyseem to provide the best results. The tumour maymetastasise to regional lymph nodes as well as lungs.Prognosis is poor with almost 50% of the patients failingloco-regionally within the first 2 years of followup[190].4.4.4.4 Clear CellOdontogenic CarcinomaICD-O:9341/1Clear cell odontogenic carcinoma was initially reportedas a clear cell odontogenic tumour [56]. As these lesionsnot only behave aggressively locally, but may also metastasise,the currently used diagnostic term clear cellodontogenic carcinoma appears to be more appropriate[43, 75]. The tumour is mostly seen in elderly patients[5].The tumour is composed of cells with clear cytoplasm.These cells form nests and strands, intermingledwith smaller islands of cells with eosinophilic cytoplasm(Figs. 4.26, 4.27). Also, squamous differentiationhas been reported [17]. Cells at the periphery ofthe nests may show palisading. The clear cells stain positivefor glycogen as well as for epithelial markers keratinAE1/AE3, cytokeratin 8/18, cytokeratin 19 and epithelialmembrane antigen (EMA) [89].The anterior mandible appears to be the site of predilection.Metastases are found in lymph nodes as well asin the lungs and the skeleton. Recurrent disease is seenin more than 50% of cases with documented follow-up.Death due to the tumour has also been reported [5, 89].Differential diagnosis includes metastatic renal cellcarcinoma, the clear cell variant of mucoepidermoidcarcinoma, and ameloblastoma with clear cells. Metastaticrenal cell carcinoma may be ruled out on clinicalgrounds. The clear cell variant of muco-epidermoidcarcinoma can be identified with stains for mucin production.Differentiation from ameloblastoma with clearcells may be problematic and it has been proposed thatthese lesions represent the same entity [16]. Clear cellcarcinoma of minor salivary gland origin is another differentialdiagnosis (see Chap. 5).4.4.4.5 Malignant EpithelialOdontogenicGhost Cell TumourICD-O:9270/3Malignant epithelial odontogenic ghost cell tumour ,also called odontogenic ghost cell carcinoma is a tumourthat combines the elements of a benign calcifying odontogeniccyst with a malignant epithelial component.Only a few cases of this tumour have been reported, thusprecluding any conclusions regarding clinicopathologicfeatures. Malignancy has been demonstrated by local aggressivegrowth and distant metastasis [84]. The tumourapparently arises most often from malignant transformationof a pre-existing benign calcifying odontogeniccyst [81].4.4.4.6 Odontogenic SarcomaICD-O:9270/3The WHO discerns between ameloblastic fibrosarcoma ,ameloblastic fibrodentino- and fibro-odontosarcomaand odontogenic carcinosarcoma [73, 181]. The ameloblasticfibrosarcoma consists of malignant connectivetissue admixed with epithelium similar to that seen inan ameloblastoma or ameloblastic fibroma [152]. If thereis also dentin, this is known as an ameloblastic fibrodentinosarcoma, and if there is also enamel, it is called ameloblasticfibro-odontosarcoma . This subclassification hasno prognostic significance [2]. These tumours may arise