Follicular hybrid cysts with infundibular, isthmic-catagen, and pilomatrical differentiation: a report of 2 patients.

The term hybrid cyst was originally coined to describe combination follicular cysts with both epidermoid and trichilemmal (pilar) epithelial zones, separated by an abrupt transition. The concept has since expanded to include many different combinations of pilosebaceous unit differentiation. Entities previously reported also include infundibular and pilomatricomal cyst, trichilemmal and pilomatricomal cyst, eruptive vellus hair cyst combined with steatocystoma or trichilemmal cyst, and trichilemmal, sebaceous, and pilomatricomal cyst. We report 2 cases of follicular hybrid cysts, all mixtures of epidermoid, trichilemmal, and matrical differentiation. The cysts, involving the ear and abdomen, occurred in one woman and one man.