A Case of Trichoepithelioma Papulosum Multiplex with Sweat Duct Differentiation: An Immunohistochemical and Electron Microscope Study

The present study demonstrated the structure of the multiple nodules of trichoepithelioma papulosum multiplex (TPM) with sweat duct differentiation taken from a 74-year-old woman. Histologically, the tumor was wellcircumscribed, and composed of several basaloid nests with palisading at the periphery, keratinous cysts, and occasional follicular papillae. Another prominent finding was the presence of some small duct-like structures, which were proven by immunohistochemistry and electron microscopy to be sweat ducts. Typically, trichoepithelioma is considered a benign neoplasm showing differentiation toward the hair follicle. We here report a unique case which showed combined differentiation toward the hair follicle and sweat duct.