Primary adenoid cystic carcinoma masquerading as syringoma of the scalp

We report a case of primary adenoid cystic carcinoma of the scalp in a 72-year-old man. It consisted of syringomalike papules scattered on an erythematous plaque that showed a loss of hair. Histologically, the papular lesion at first showed numerous tadpole-like tubular structures similar to those found in syringoma. Subsequent histologic studies over 2 years revealed the presence of numerous cribriform tumor masses penetrating into the subcutis, reaching the galea aponeurotica. Immunohistochemically, the neoplastic cells showed no staining with either polyclonal (P) or monoclonal (M) antibodies to carcinoembryonic antigen. M-cytokeratin, M-vimentin, and P-S-100 protein antibodies were positive only focally as were other antibodies, including anti-actin, anti-human lactalbumin, anti-beta 2 microglobulin, and breast cancer--associated antigens. The neoplastic cells showed no binding to lectins that characteristically react with the sweat apparatus, except for concanavalin A (con A) and peanut agglutinin (PNA), although the striking histopathologic resemblance to syringoma suggested its histogenic relation to eccrine glands initially.