Basal cell adenocarcinoma of minor salivary and seromucous glands of the head and neck region.

Basal cell adenocarcinoma of salivary glands is an uncommon and recently described entity occurring almost exclusively at the major salivary glands. This report provides an overview of the clinicopathologic profile of this neoplasm by including the personal experience on the clinical features, microscopic and ultrastructural characteristics, proliferation activity, and DNA tumor patterns of 12 lesions occurring at the minor salivary glands of the head and neck region, where basal cell adenocarcinoma is probably an underecognized entity, previously reported under different designations. Basal cell adenocarcinoma predominates at the seventh decade without sex preference. The tumors affecting the minor salivary glands occur most frequently at the oral cavity (jugal mucosa, palate) and the upper respiratory tract. The prevalent histologic tumor pattern is represented by solid neoplastic aggregates with a peripheral cell palisading arrangement frequently delineated by basement membrane-like material. The neoplastic clusters are formed by two cell populations: the small dark cell type (that predominates) and a large cell type. Necrosis, either of the comedo or the apoptotic type, is a frequent finding. Perineural growth occurs in 50% of the cases and vascular permeation in 25%. Immunohistochemistry identifies a dual differentiation with a reactivity pattern indicative of ductal epithelial and myoepithelial differentiation, which can be confirmed by electron microscopy. The differential diagnosis of the neoplasm includes its benign counterpart, the basal cell adenoma, solid variant of adenoid cystic carcinoma, undifferentiated carcinoma, and basaloid squamous carcinoma. The tumors recur more frequently than lesions originating in major salivary glands. Mortality is associated with the anatomic site of the lesion, advanced stage, residual neoplasia at surgery, and tumor recurrence. The importance of recognizing basal cell adenocarcinoma outside major salivary glands is related to the clinical behavior of the neoplasm that seems to be less indolent than that of tumors arising in major salivary glands.