Plaque-Like Pilar Sheath Acanthoma: Histopathologic and Immunohistochemical Study of 3 Unusual Cases.

Pilar sheath acanthoma is an uncommon, benign follicular neoplasm that frequently presents as a solitary lesion. This neoplasm usually appears on the skin around the upper lip of elderly patients. Histopathologically, the neoplasm usually shows a cystic configuration with epithelial lobules resembling to those of the outer root sheath of the hair follicle at the level of the isthmus emanating radially from the cyst wall. We present 3 peculiar cases of a pilar sheath acanthoma showing a plaque-like architecture because the lesions exhibited a horizontal configuration. To our knowledge, there are no previously reported examples of plaque-like pilar sheath acanthoma.