A Histopathological Investigation of Horn Cysts Formation in Seborrheic Keratosis: Horn Cysts Originate from the Intra-epidermal Adnexal Epithelium

Abstract

We observed the relationship between horn cysts which are one of the most important findings in seborrheic keratosis, and the intra-epidermal adnexal epithelium in 481 cases of seborrheic keratosis. In 280 out of 481 cases (58.2%), the horn cysts had continuity to normal hair follicles or hairs were seen with in the horn cysts. In 33 out of 481 (6.9%), the horn cysts had continuity to normal eccrine ducts. In 13 out of 481 cases (2.7%), the horn cysts had relationships with both hair follicles and eccrine ducts. From those findings, we speculate that the horn cyst of SK is not formed by invagination of the epidermis, but rather by proliferation of neoplastic cells in the adnexal epithelium.