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. The treatment consisted of left maxillary resection followed by reconstruction. Cellular features of malignancy in the surgical specimen confirmed the diagnosis of ameloblastic carcinoma. This case of an aggressive ameloblastic carcinoma of the maxillary gingiva that presented with an unusual histological pattern illustrates that these tumors can create a diagnostic challenge that may require extensive surgical sampling and/or removal to establish the diagnosis. Immunohistochemically analyzed expression of bcl-2 protein, cytokeratins CAM 5 and 6, and Ki-67/MIB-1 antigen serve to characterize the cyto-differentiation and cellular activity of ameloblastic carcinoma.