Hair follicle nevus: case report and review.

Hair follicle nevus has been variously defined as a specific type of neoplasm with follicular differentiation or as a synonym for trichofolliculoma; the latter view has predominated in recent years. We report a nodular lesion that was identified histopathologically as a hamartoma with follicular differentiation and that systematic serial sectioning showed not to be a trichofolliculoma. After reviewing previous descriptions of lesions diagnosed as hair follicle nevus, and in the light of our own observations, we believe that hair follicle nevus is a distinct type of adnexal hamartoma.