Trichilemmal cyst: report of a case in which the cyst was connected with the epidermis by an epidermal canal.

An 87-year-old Japanese woman with a trichilemmal cyst (TC) on the subnasal area is described. Histopathological examination revealed that the cyst was connected with the overlying epidermis by an epidermal canal. This has suggested that the pathogenesis of TCs could be that they originate from the isthmus or lower portion of the hair follicle.