Papillary eccrine adenoma: an ultrastructural and immunohistochemical study.

A 45-year-old African American man presented with a small, solitary, nonulcerated cutaneous lesion of the right thigh of many years duration, which was excised. Light microscopically, the lesion consisted of an oval, well-circumscribed, intradermal proliferation of tubules, which were often dilated and lined by a double layer of tumor cells with conspicuous intraluminal papillations. Ultrastructurally, there was evidence of both intradermal eccrine duct and eccrine secretory coil differentiation. Although the majority of tumor cells resembled cells of the intradermal eccrine duct, occasional myoepithelial tumor cells and rare tumor cells having secretory granules and resembling dark mucous cells were indicative of eccrine secretory coil differentiation. The positive immunohistochemical staining for S-100 protein, CEA, EMA, and vimentin supported these ultrastructural findings.