Trichoblastoma with Apocrine and Sebaceous Differentiation

Abstract
Trichoblastoma is a rare, benign tumor that differentiates toward the hair germ, the embryonic precursor of a hair follicle. Several cases of trichoblastoma showed multiple differentiation toward more than one type of adnexal structure. We report a case of a trichoblastoma, which had developed on the scalp as a solitary 1-cm nodule 3 years ago. A histologic examination indicated that the specimen had features of multiple differentiation. In particular, there were occasional foci of decapitation secretion, as well as cells with web-like and bubbly cytoplasm suggesting seboblasts, and a sebaceous duct-like structure. In addition, there were occasional germinative cells in the palisade, and scattered hair papilla-like structures showing follicular differentiation. An immunohistochemical study showed that the neoplasm, or areas in it, stained positive for low molecular cytokeratin, high molecular cytokeratin, EMA, S-100, and GCDFP-15. This is an unusual case of a trichoblastoma with apocrine and sebaceous differentiation.

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