A salivary gland adenocarcinoma mimicking a microcystic adnexal carcinoma

The microcystic adnexal carcinoma (MAC) is a rare, slow-growing but locally aggressive neoplasm arising in the midface and lips of middle-aged adults. The MAC is histologically characterized by deeply infiltrating nests and islands of basaloid or squamous cells forming cysts and ductal structures, proliferating in a dense sclerotic stroma and occasionally exhibiting perineural invasion. We describe a salivary gland adenocarcinoma arising in the lower lip, characterized by ductal structures and cords, 3-5 cell layers in thickness, set in a dense fibrous stroma and also invading nerves, thus mimicking a MAC in both its clinical and its histopathologic appearance. The diagnostic dilemma presented by this lesion is discussed, along with a differential diagnosis and brief review of the literature.