Trichoblastic fibroma. A clinicopathologic study of three cases.

Three cases of trichoblastic fibroma, a rare benign skin tumor of hair follicle origin, are reported. On clinical examination, solitary, mobile, subcutaneous nodules with normal overlying skin were found on the vulva (one case) and scalp (two cases) in women aged 57, 46, and 19 years, respectively. On microscopic examination, the tumors were composed of complex nests and strands of basaloid, focally keratinized epithelium arranged in a moderately cellular fibroblastic stroma. No connection with the overlying epithelium or adjacent adnexal structures was observed. Immunohistochemical staining supported a trichogenic origin for these tumors. Trichoblastic fibromas are histologically distinctive lesions that should be distinguished from other tumors of follicular origin and from keratotic basal cell carcinoma.