A Case of a Hybrid Cyst Composed of an Epidermal Cyst and a Pilomatricoma

Woo, Sang Hyuk; Yu, Dong Soo; Song, Hae Jun; Oh, Chil Hwan

Abstract

It is known that different parts of a pilosebaceous unit, namely the infundibulum, isthmus, sebaceous ducts, and bulbar or inferior portion, can give rise to a variety of cutaneous cysts, such as epidermal, trichilemmal, steatocystoma, or pilomatricoma. In rare instances, a cyst can arise from various portions of a hair follicle and combine to form a hybrid cyst. The pathogenesis of this lesion is uncertain. Studying the clinicopathological features of hybrid cysts helps us to understand the pathogenesis of disease which can arise from pilosebaceous units. Epidermal cysts and pilomatricoma are recognised to be clinically similar but histologically distinct entities. We present a case of a patient with a solitary nodule on the posterior neck, showing combined histologic features of both an epidermal cyst and pilomatricoma.