Folliculo‐sebaceous cystic hamartoma is a trichofolliculoma at its very late stage

Abstract

Folliculo-sebaceous cystic hamartoma (FCH) was described as an entity recently and was defined as an adnexal hamartoma, showing above all an infundibular cystic structure linked to many sebaceous lobules. Differentiation toward the inferior segment of the hair follicle also occurs, although to a markedly lesser degree. Signs of regression and rest corresponding to the normal follicular cycle are often apparent in these follicular proliferations. Therefore so-called FCH has much in common with the newly described late stage of trichofolliculoma, which also exhibits an infundibular cyst and sebaceous and follicular differentiation with various signs of catagen and telogen. Comparing our 8 cases of FCH and 31 cases of trichofolliculoma, we came to the conclusion that FCH is the very late stage of trichofolliculoma. This stage could be characterized by a nearly complete regression of the transient follicular epithelium, whereas concurrent growth and maturation of sebaceous elements appear.