Cytomorphology and immunohistochemistry of a recurrent clear cell odontogenic carcinoma with molecular analysis: A case report with review of literature.

Clear cell odontogenic carcinoma (CCOC) is a rare, odontogenic tumor of the jaws with mandibular involvement usually present in sixth decade of life with female preponderance. It is classified as a malignant tumor of odontogenic origin in 2005 by the World Health Organization because of its aggressive and destructive growth capacity and potential to metastasize. It needs to be distinguished from other primary and metastatic clear cell tumors of the oral and maxillofacial region. Recently, CCOCs have been noted to harbor a Ewing sarcoma breakpoint region 1 gene RNA-binding protein 1 (EWSR1) and activating transcription factor (ATF) gene translocation. To date, cytologic features of only one case have been reported in the literature. We report an additional case of 55-year-old woman with enlarging mass in the left mandible. This report describes cytologic and immunohistochemical features of CCOC with positive EWSR1 gene rearrangements by fluorescence in situ hybridization (FISH). As diagnosis of CCOC is challenging on fine-needle aspiration, immunohistochemistry and FISH analysis are very useful diagnostic tool in clear cell lesions of mandible.