Salivary gland tumors: revision of 391 cases according to the new WHO classification.

We reviewed 391 cases of salivary gland tumors collected in a 13 year period at the Institute of Pathological Anatomy of the University of Modena, according to the new WHO classification (1991). A diagnosis of pleomorphic adenoma was changed in adenoid cystic carcinoma. Within malignant tumors, 16 cases were reclassified, and new entities, such as polymorphous low-grade adenocarcinoma, papillary cystoadenocarcinoma and salivary duct carcinoma were introduced. Mucoepidermoid carcinomas were subdivised in low-grade and high-grade tumors, but at the follow-up histological grade did not correlate with clinical behaviour of the lesions.