CLINICAL AND THERAPEUTIC FEATURES OF POLYMORPHOUS LOW-GRADE ADENOCARCINOMA

Polymorphous low-grade adenocarcinoma, also known as terminal duct or lobular carcinoma, was first described in two clinical case series in 1983. Before that time most of these neoplasms were diagnosed as benig n salivary gland neoplasms including pleomorphic adenomas, variants of monomorphic adenomas, or salivary malignant conditions including mali gnant pleomorphic adenomas, adenoid cystic carcinomas, and adenocarcin oma not otherwise stated. This neoplasm with few exceptions originates in minor salivary gland tissue of the posterior hard and soft palates or buccal mucosa. It is characteristically slow to enlarge; clinical reports show the neoplasm present for many years before diagnosis. We have evaluated the clinical and microscopic features of 15 cases from the archives of The University of Iowa Surgical Oral Pathology Laborat ory and added these to published case reports. A total of 204 cases we re evaluated with a female/male ratio of almost 2/1. Forty-nine percen t originated in palatal mucosa. Polymorphous low-grade adenocarcinomas arising from pleomorphic adenomas or de novo have been reported withi n major salivary glands and outside the oral cavity. A 17% recurrence rate was found with a regional metastasis rate of 9%. Five cases had m ultiple recurrences, and 13 recurrences were at or beyond 5 years afte r the initial diagnosis. Regional node metastases were identified at t he time of initial treatment or at the time of recurrence in 9% of cas es in which follow-up data were specified.