PP101: Odontogenic carcinomas – Validity of variants?

Abstract

Odontogenic tumours are broadly classified into benign and malignant. Malignant Odontogenic Tumours (MOTs) comprise the first category of the 2005 WHO classification of odontogenic tumours. Odontogenic carcinomas encompass a large portion of MOTs which include malignant ameloblastomas, ameloblastic carcinomas, primary intraosseous squamous cell carcinomas, clear cell odontogenic carcinomas and malignant ghost cell odontogenic carcinomas. The occurrence of this set of odontogenic tumours is extremely rare. Only a few dozens have been reported in the English literature so far. The putative source of the epithelium giving rise to an intraosseous carcinoma is the epithelium involved in odontogenesis, these lesions are often designated as odontogenic carcinomas. These tumors may theoretically arise (1) from the lining of odontogenic cysts, (2) from other epithelial odontogenic tumors, or (3) de novo from presumed odontogenic rests. Odontogenic carcinomas are central lesions occurring most often in the mandible which arise from the remnants of the dental lamina or reduced enamel epithelium. They exhibit an aggressive nature and are associated with extensive jaw bone destruction. Involvement of lymph node and distant metastases may occur early in the course of the disease. We would like to share our experience with two such cases from our department archives. Both lesions developed from a preexisting benign counterpart or most probably from a prior odontogenic cyst or tumour. One was diagnosed as an ameloblastic carcinoma ex ameloblastoma which began as a benign ameloblastoma, which on repeated occurrences, acquired malignant features. The other case of interest was an odontogenic carcinoma. Though the histopathology showed features akin to a salivary ductal carcinoma and of a lesion arising de novo, we believe that it developed from a benign cyst or tumour. This paper reveals our findings on evaluating these cases using routine H&E and various immunohistochemical markers to infer from and to draw conclusions.