Sclerosing-sweat-duct (microcystic adnexal) carcinoma--a tumor from a single eccrine origin.

A patient with a sclerosing-sweat-duct carcinoma of the upper lip is reported. Histologically the tumour showed solid islands and strands of squamous cells and sparse small ductal structures, some of them containing central cores of dense eosinophilic keratin. All this was embedded in a sclerotic stroma. These features, in addition to positive immunoreactivity for carcinoembryonic antigen (CEA) in the lumina of small ducts, and the presence of S-100 protein-positive cells in some cords and ducts, are consistent with the notion that this tumour exhibits differentiation toward eccrine sweat structures.