Salivary gland double tumor: synchronous ipsilateral pleomorphic adenoma and acinic cell carcinoma of the parotid gland.

A 44-year-old woman underwent a partial parotidectomy for a slowly enlarging parotid mass diagnosed by fine needle aspiration biopsy as a pleomorphic adenoma. Though macroscopically recognized to be composed of two nodules, differing to some extent from one another, the mass appeared to constitute a single tumor. The microscopic examination disclosed two disparate neoplasms, which were separated from each other by a thin fibrous band. The larger of the two nodules was a pleomorphic adenoma and the smaller one an acinic cell carcinoma. The metachronous--and, even more, the synchronous--occurrence of two histologically different tumors in one major salivary gland is an exceptional and probably coincidental event.