Salivary gland adenocarcinomas: a clinicopathologic analysis of three distinctive types.

Myoepithelial cells play an important role in the histogenesis of adenocarcinomas arising from the salivary duct unit nearest the acini. Prototype adenocarcinomas arising from the intercalated duct are the terminal duct carcinoma and the epimyoepithelial carcinoma, both typically low-grade malignancies. Those salivary adenocarcinomas arising from the larger nonintercalated excretory ducts do not manifest myoepithelial cells in their composition. A prime example is the salivary duct carcinoma, which is a high-grade malignancy. These adenocarcinomas have distinctive clinical and pathologic features and they should be recognized by the examining pathologist. Because of the potential clinical confusion between terminal duct carcinoma and salivary duct carcinoma when rendered as a diagnosis, each should be further qualified, eg, by adding high or low grade.