Folliculocystic and Collagen Hamartoma: A New Entity?

Abstract

Folliculocystic and collagen hamartoma is a newly described complex hamartoma characterized by abundant collagen deposition, concentric perifollicular fibrosis, and keratin- filled infundibular cysts that are visible on histopathological examination. Here, we report the case of a 19-year-old Korean man who had large brownish infiltrated plaques with numerous follicular comedo-like openings and subcutaneous cystic masses on his right temporal scalp and ear since birth. Histopathological examination showed abundant collagen deposition in the dermis that extended up to the subcutaneous fat layer, multifocal infundibular cysts packed with keratin, and perifollicular inflammation and fibrosis. Hence, we describe a new type of hamartoma with folliculocystic and collagen components but without tuberous sclerosis.

Keywords: Folliculocystic and collagen hamartoma; Tuberous sclerosis.

Fig. 1. Brownish infiltrated plaques with numerous follicular comedo--like opening and subcutaneous cystic masses on the right temporal scalp and ear.

Fig. 2. (A) Variable-sized multifocal infundibular cysts packed with keratin and comedones (×40). (B) Abundant, thick, eosinophilic collagen deposition in the dermis extending into the subcutaneous fat layer as fibrous strands (×40). (C) Perifollicular concentric fibrosis (×100). (D) Concentric fibrosis also involved some small and medium vessels in the surrounding tissue (×100). A~D: H&E.

Fig. 3. Masson's trichrome staining showed increased collagen bundles and variable concentric fibrosis of hair follicles and other skin appendages (Masson's trichrome, ×100).