We describe a case of giant trichoblastoma that had been present for m
any years on the scalp of a 69-year-old man. The specimen was examined
histopathologically, immunohistochemically, and ultrastructurally. Hi
stopathologic examination showed that neoplastic cells were arranged i
n different patterns from area to area, including rippled, adenoid, an
d palisading patterns. In some areas of the neoplasm, foci of sebaceou
s differentiation were also present. The ultrastructural characteristi
cs of neoplastic cells support the notion that trichoblastomas are neo
plasms composed mostly of follicular germinative cells.