Ameloblastic carcinoma of the maxillary sinus.

Ameloblastic carcinoma is a very rare malignant odontogenic neoplasm of the mandible and maxilla, accounting for some 66 reported cases. The case of a 68-year-old man who presented a fistula with orosinus communication of 14-year duration that, after anti-aggregant therapy, began bleeding is reported. The initial microscopic evaluation of the biopsy and radiographic findings were consistent with benign peripheral ameloblastoma without cellular atypia and extensive fields of acantomatous pattern, but immunohistochemical investigation found strong positivity for Bcl-2, cytokeratins CAM 5 and 6, and for Ki-67/MIB-1, changing our diagnosis.