Follicular hybrid cyst on the cheek: A combination of infundibular, isthmic, and pilomatrical differentiation

Abstract

A hybrid cyst is a rare condition which includes any type of cyst arising from the various parts of the pilosebaceous unit. We report a case of hybrid cyst with infundibular, isthmic, and pilomatrical differentiation. A 12-year-old boy presented with a mass on the right cheek. The physical examination revealed an oval-shaped, dark-gray protruding mass with dimensions of 0.9 cm×0.6 cm that was non-tender to palpation. The mass was totally excised. The diagnosis of a hybrid cyst was confirmed by histological evaluation. It was a well-encapsulated mass and showed combined histologic features of infundibular, isthmus, and pilomatrical differentiation. The hybrid cyst is a follicular cyst that includes two or more components of a cystic lesion arising from the pilosebaceous unit. Occasionally, there have been reports of hybrid cysts consisting of two components in differentiation, but those showing more than two components of differentiation have been extremely rare. The pathogenesis of this unusual disease is not yet known.

A Rare Hybrid Skin Cyst of the Scalp With Pilar and Apocrine Features

“…This term has since been expanded to include any type of cyst that has a combination of two or more components of the folliculo-sebaceous-apocrine unit, which may include infundibulum, isthmus, or lower portion (hair bulb) of the hair follicle, sebaceous gland, and apocrine gland [ 2 ]. Although most reported hybrid cysts are those that contain a combination of epidermal and pilar elements, there have been rare reports of cysts such as hybrid pilomatricoma and epidermal cysts, as well as hybrid eruptive vellus hair cyst and steatocystoma, all derived from a hair follicle [ 2 , 3 ]. However, hybrid pilar and apocrine cysts are only rarely encountered in the literature.…”