[Polymorphous low-grade adenocarcinoma of the minor salivary glands. Seven cases]

Seven cases of polymorphous low-grade adenocarcinoma of the minor salivary glands are reported. This fairly recently described tumor, which is not exceptional, is characterized by a polymorphous architecture, fairly uniform cytologic features, and a marked tendency to infiltrate neighboring structures with perineural spread in virtually every case. Immunohistochemical and ultrastructural studies reported in the literature have demonstrated that the tumor cells exhibit epithelial and myoepithelial differentiation. These tumors probably arise from reserve cells in terminal ducts. The histologic study should eliminate two other tumors that carry a very different prognosis, i.e., pleiomorphic adenoma and the tubular, cribriform variety of cystic adenoid carcinoma. Low-grade polymorphic adenocarcinomas grow slowly. Recurrences are infrequent. Metastases are rare and involve only regional lymph nodes. The morphologic features and course of these tumors explain the term "low-grade polymorphous adenocarcinoma" used to designate them.