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Desmoplastic Trichoepithelioma

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Comments:
Presentation: Desmoplastic trichoepithelioma (aka Sclerosing Epithelial Hamartoma) presents as a solitary asymptomatic slow growing lesion on face (cheek, chin, or forehead) and neck of young adults (F>M). It is a firm annular lesion, white or yellow in appearance, with a depressed center and elevated edges. The size ranges from 0.5 to 1.0 cm in diameter. Unlike multiple trichoepitheliomas, familial occurrence is not seen.

Histology: The histologic hallmarks of desmoplastic trichoepithelioma are thin epithelial strands and keratinous cysts in a background of desmoplastic stroma. The epithelial strands, which may be linear or branching, are composed of basaloid cells and often connect to the cyst walls. Calcification and keratin-induced foreign body giant cell reaction is commonly seen. Sometimes, there is even bone formation. The overlying epidermis is normal, atrophic or slightly thickened.

The stroma is dense and frequently hyalinized. Features that are absent include mitotic activity, pleomorphism, peripheral palisading, and perineural infiltration. The tumor cells are negative for p53 and bcl-2. MIB-1 proliferation index is low. Stroma contains CD34+ cells. Desmoplastic trichoepithelioma sometimes coexists with an intradermal nevus.

Image courtesy of: Univ. of Michigan Dept. of Pathology; used with permission

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