Salivary terminal duct carcinoma

Polymorphous low-grade adenocarcinoma: glial fibrillary acidic protein staining in the differential diagnosis with cellular mixed tumors

Polymorphous low-grade adenocarcinoma is a recently recognized salivary gland carcinoma arising primarily within the oral cavity. Most of these tumors are readily diagnosed; occasionally, however, they may be confused histologically with cellular mixed tumors. The difficulty stems from the bland cytologic nature of cellular mixed tumors and their organizational diversity, together with the irregular pushing growth at their interface with adjacent soft tissues, on histologic examination. Because of this diagnostic problem, we evaluated the use of glial fibrillary acidic protein localization in the differential diagnosis of polymorphous low-grade adenocarcinoma and cellular mixed tumor. Twelve oral polymorphous low-grade adenocarcinomas (polymorphous low-grade adenocarcinoma) and twelve cellular mixed tumors were selected and stained for glial fibrillary acidic protein (glial fibrillary acidic protein) using a strept-avidin-biotin system and examined independently by each investigator. In addition, five tumors with limited material (three cellular mixed tumors and two polymorphous low-grade adenocarcinoma) from the consultation service of one author were evaluated using the same techniques. Two polymorphous low-grade adenocarcinoma stained positive in very focal areas and only in the epithelial component; staining did not occur in the stroma. Fourteen of fifteen mixed tumors focally to diffusely expressed glial fibrillary acidic protein. Only one tumor did not express glial fibrillary acidic protein. In mixed tumors with only focal staining, the most helpful differential diagnostic feature was positive staining of the mesenchyme-like cells adjacent to epithelial nests. We did not find this latter staining pattern in any of the polymorphous low-grade adenocarcinoma.

Orbital and skin metastases in a polymorphous low grade adenocarcinoma of the salivary gland

We report the previously undocumented development of an orbital metastasis and skin metastases in a patient with polymorphous low grade adenocarcinoma (PLGA) 15 years after initial presentation. The clinical course, treatment and changing histological features are discussed.

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 benign salivary gland neoplasms including pleomorphic adenomas, variants of monomorphic adenomas, or salivary malignant conditions including malignant pleomorphic adenomas, adenoid cystic carcinomas, and adenocarcinoma 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 Laboratory and added these to published case reports. A total of 204 cases were evaluated with a female/male ratio of almost 2/1. Forty-nine percent originated in palatal mucosa. Polymorphous low-grade adenocarcinomas arising from pleomorphic adenomas or de novo have been reported within major salivary glands and outside the oral cavity. A 17% recurrence rate was found with a regional metastasis rate of 9%. Five cases had multiple recurrences, and 13 recurrences were at or beyond 5 years after the initial diagnosis. Regional node metastases were identified at the time of initial treatment or at the time of recurrence in 9% of cases in which follow-up data were specified.