Monomorphic adenomas of the major and minor salivary glands. Report of twenty-one cases and review of the literature.

Monomorphic adenomas are benign salivary gland tumors that have a predilection for development in the upper lip and parotid gland. Typically, patients are older persons (mean age, 61 years), but a broad age range (32 to 87 years) has been reported in the literature. Adequate treatment consists of superficial or total parotidectomy (depending on extent and location of the tumor) for parotid lesions and excision with a limited border of normal tissue for minor gland tumors. Uniform cellularity, lack of myxoid or chondroid features, and a tendency for multicentric origin are features which separate these tumors from pleomorphic adenomas. Monomorphic adenomas have been mistakenly diagnosed and treated as adenoid cystic carcinomas. Close attention to cytologic detail, histomorphology, and growth pattern at the periphery are important in separating these tumors.