Abstract:

A case of benign follicular neoplasm-trichogerminoma-is reported. A 48-year-old man presented with a 10-year history of asymptomatic subcutaneous nodule in the chest. Histological examination revealed a well-circumscribed lesion composed of variously sized lobuli and cysts in the deep dermis and separated from the surrounding tissue by a fibrous capsule. Most lobuli consisted of concentrically arranged clear cells in the central area and basophilic cells in a palisade arrangement in the peripheral area. The tumor cells displayed a multi-directional differentiation toward hair bulb, inner root sheath, outer root sheath and infundibulum of hair follicles. Immunohistochemically, the tumor cells expressed AE1/AE3, CK5/6 and CK17, but were negative for CK20 or CK7. There was a sharp contrast in immunohistochemical findings between the central clear cells and peripheral basophilic cells. Based on the histological and immunohistochemical features, a diagnosis of trichogerminoma was made.

Key words: hair follicular neoplasm