A case of malignant calcifying epithelial odontogenic tumor

Background: Calcifying epithelial odontogenic tumor (CEOT) is a rare tumor that accounts for about 1% of the odontogenic tumors. We report a case of malignant CEOT with nodal metastasis and describe its cytological features. Case: The patient was a 56-year-old man with CEOT in his mandible. The tumor recurred four times in three years after the first resection. Cytologically, the third recurrent tumor was diagnosed as malignant CEOT, with small to large tumor cells present singly or in clusters. The small tumor cells had round to oval nuclei with prominent nucleoli, increased chromatin, and a high N/C ratio. The large tumor cells were mononucleated or multinucleated with abundant basophilic cytoplasm, increased chromatin and prominent nucleoli. Lamellar structures and perinuclear halos were observed in the cytoplasm. These cytologic findings were very similar to those of squamous cell carcinoma. Histologically, the tumor cells in the primary tumor showed solid proliferation and were round to oval in shape with eosinophilic cytoplasm and pleomorphic nuclei. Multinucleated cells were rare. Calcification and amyloid deposition were observed in the primary tumor but were not found in any of the recurrent tumors. The tumor cells in the third recurrent tumor were interpreted as malignant CEOT based on the marked cellular atypia and frequent mitotic figures. Vascular invasion was also evident. Three years after the fourth recurrence, metastasis to the supraclavicular lymph node was found. Conclusion: Cytologically, pleomorphic cells of a squamoid type with amyloid deposition and calcification are characteristic features of CEOT. Based on the cytologic findings alone, it may be very difficult or even impossible to determine whether the tumor is benign or malignant. Physicians must take care not to misdiagnosc benign CEOT as a malignant tumor, such as squamous cell carcinoma or mucoepidermoid carcinoma.