Basal cell adenocarcinoma is a rarely encountered malignant lesion of the salivary glands. The term BCACwas mentioned first by Gnepp1in 1988 and then by Luna et al2in 1989 but was best described in the literature by Ellis and Wiscovitch3in 1990. This neoplasm, which appeared in the World Health Organization classification of salivary tumors in 1991,4is composed of 2 subtle cell types: (1) smaller basloid cells with scant cytoplasm and dark nuclei and (2) slightly larger polygonal basaloid cells with eosinophilic cytoplasm.5Both of these cell types have a basaloid appearance on routine hematoxylin-eosin staining, hence the name BCAC.6Four histomorphological architectural patterns have been described (solid, membranous, tubular, and trabecular), with the solid form being the most common.5The membranous pattern is characterized by excessive production of basal lamina material. The lesion is thought to arise de novo and histologically resembles basal cell adenoma but with an invasive growth pattern and the potential for metastasis. Vascular and perineural invasion has been described in about one fourth of cases.7There is variability in the degree and amount of atypia and mitotic activity, although, generally, atypia and mitotic activity are minimal and are not required for diagnosis.8In fact, according to Ellis and Wiscovitch,3the key feature that distinguishes this malignant lesion from its benign counterpart is an infiltrative growth pattern showing extension beyond the main tumor mass. While this feature helps to distinguish basal cell adenoma from BCAC, the differential diagnosis is broader.
Pathology Quiz Case 1: Diagnosis. Arch Otolaryngol Head Neck Surg. 2010;136(3):312-313. doi:10.1001/archoto.2010.8-b