pilar cyst /pī′lər/ [L, pilus, hair; Gk, kystis, bag] , an epidermoid cyst of the scalp. Its keratinized contents are firmer and less cheesy than the material in epidermoid cysts found elsewhere. The cyst originates from the middle part of the epithelium of a hair follicle. Treatment is surgical excision. Also called wen. Compare epidermoid cyst.