Pilomatricoma Combined with Epidermoid Cyst

Cho, Soyun; Whang, Kyu Kwang; Hahm, Jeong Hee

Abstract

A 22-year-old woman with no history of trauma or other diseases presented with a slowly enlarging firm nodule with a central pointed opening on the right chest. An excisional biopsy revealed a pilomatricoma associated with an epidermoid cyst. Histopathologically, an epidermoid cyst located in the deep dermis was lined mostly by keratin-forming stratified squamous epithelium but focally had columns of shadow cells that projected from the epithelial lining of the cyst into the lumen. The lumen also contained masses of shadow cells, unattached to the epithelial lining. In the stroma surrounding the cyst, numerous masses of shadow cells with giant cell reaction and focal calcification were seen, which were in turn surrounded by a connective tissue capsule. These features are similar to those seen in infundibular cysts associated with Gardner's syndrome. Since epidermoid cysts and pilomatricomas originate in common from the pilosebaceous unit and pilomatricomas begin as infundibular matrix cysts, we suggest that they can occur simultaneously, although rarely, in a healthy person.