Acinic cell carcinoma of the palate: case report and immunohistochemical observation.

We report a rare case of acinic cell carcinoma of the palate in a 63-year-old Japanese woman. Clinical examination demonstrated a firm, mobile mass without regional lymph-adenopathy. Histopathologically, the tumor was composed of large, polyhedral or round cells with basophilic granular cytoplasm (serous acinar-like cells) and reticular or clear cytoplasmic cells. These tumor cells were positive for the periodic acid-Schiff reaction, but negative for alcian blue. The tumor nests were separated by thin vascular tissue and incompletely encapsulated. Immunohistochemically, the tumor cells exhibited positive reactivity for alpha-amylase, lactoferrin, secretory component, S100 protein, and epithelial membrane antigen, but were negative for actin, glial fibrillary acidic protein, keratin, and carcinoembryonic antigen. These results suggest that this tumor is well differentiated into serous acinar cells and that the reticular and clear cytoplasmic cells are a modified form of these cells.