Benign sebaceous neoplasm with prominent epidermal component.

A 65-year-old woman presented with a solitary nodule within an erythematous plaque in her right groin. Histopathologic examination showed central lobular proliferation of basaloid cells admixed with mature sebaceous cells and a lateral extensive intraepidermal component composed mostly of lobules of mature sebocytes consistent with intraepidermal epithelioma with sebaceous differentiation and focal invasion. Although various cutaneous neoplasms may show an intraepidermal growth pattern, extensive sebaceous differentiation in such a neoplasm, as seen in this case, has not been described. Electron-microscopic study revealed that the basaloid cells have features of pluripotential cells. This observation supports the previously reported concept that intraepidermal epithelioma may be composed of a group of heterogeneous tumors with various degrees and lines of differentiation. Additionally, sebaceous epithelioma/adenoma should be considered in the differential diagnosis of the cutaneous neoplasms with an intraepidermal growth pattern.