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

Abstract

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.

Current Diagnosis and Treatment Options for Cutaneous Adnexal Neoplasms with Follicular Differentiation

“…Some authors suggest that this tumor is a benign follicular hamartoma. There are no known genetic abnormalities described in patients with this neoplasm [ 91 ].…”

“…Pilar sheath acanthoma is rare. It typically affects middle-aged and elderly people (age range: 30–76 years), with no sex predilection [ 91 ].…”

“…It is asymptomatic, small flesh-colored nodule (diameter 0.3–0.5 cm). The lesion has two components—a superficial infundibular component and a deeper component made up of solid epithelial lobules, which show keratinization similar to that of the outer root sheath at the level of the isthmus of the hair follicle [ 2 , 91 ].…”