Multiple malignant salivary gland neoplasms: mucoepidermoid carcinoma of palate and adenoid cystic carcinoma of floor of mouth.

Salivary gland tumors usually occur as single lesions. To have more than one tumor is unusual. We report a case of an adult male who presented with a mucoepidermoid carcinoma involving the minor salivary glands of the palate at age 57 years, followed by an adenoid cystic carcinoma of the floor of mouth at age 63 years. The patient later succumbed to non-Hodgkin lymphoma at age 72 years. There are 31 acceptable cases of multiple malignant salivary gland neoplasms reported in the world literature. Multiple malignant tumors of the same histologic type are more common than those of different histologic type. Bilateral acinic cell adenocarcinoma was the most frequent combination of multiple salivary gland malignancy, accounting for 14 cases (10 synchronous and four metachronous). All involved the parotid glands bilaterally with the exception of one case that involved parotid and submandibular gland. Polymorphous low-grade adenocarcinoma accounted for three of the four cases of multiple malignant tumors involving minor salivary glands. Individuals with a history of malignancy are at risk for the development of additional malignant tumors and should receive appropriate clinical follow-up.