Primary Adenoid Cystic Carcinoma of the Skin

An adenoid cystic carcinoma of the skin was compared with three similar neoplasms of salivary glands and with an adenoid basal cell carcinoma, from unrelated cases. The histological and immunocytochemical details of these tumors were analyzed in an attempt to determine whether or not their differing clinical behaviors would be reflected in pathologic dissimilarities. Although the single adenoid cystic carcinoma of the skin did not recur or metastasize over a 10-year follow-up period, its morphologic and biochemical features were identical to those of biologically aggressive salivary gland tumors. All four adenoid cystic carcinomas contained carcinoembryonic antigen, epithelial membrane antigen, salivary-type amylase, and alpha-lactalbumin, and all bound peanut agglutinin. Three of four expressed positivity for S100 protein, and two contained low-molecular-weight cytokeratin. In contrast, none was immunoreactive for beta-2-microglobulin, and only one displayed blood group isoantigen positivity. The adenoid basal cell carcinoma was negative for all immunological determinants, but it bound peanut agglutinin. Although these results should be regarded as preliminary, it appears that adenoid cystic carcinoma is a pathologically distinct and uniform entity, whether it occurs in the skin or in salivary glands. However, the clinical behavior of this tumor cannot be predicted on the basis of immunohistochemical or morphological studies. Finally, adenoid basal cell carcinoma is histopathologically and immunocytochemically separable from cutaneous adenoid cystic carcinoma.