Original StudyPlaque-Like Pilar Sheath Acanthoma: Histopathologic and Immunohistochemical Study of 3 Unusual CasesJo-Velasco, Margarita MD*; Corrales-Rodríguez, Araceli MD*; Francés-Rodríguez, Laura MD*; Alegría-Landa, Victoria MD*; Eraña-Tomás, Itziar MD†; Rütten, Arno MD‡; Requena, Luis MD*Author Information *Departments of Pathology and Dermatology, Fundación Jiménez Diaz, Universidad Autónoma, Madrid, Spain; †Department of Pathology, Hospital Universitario de Guadalajara, Guadalajara, Spain; and ‡Laboratory of Dermatopathology, Friedrichshafen, Germany. Reprints: Luis Requena, MD, Fundación Jiménez Díaz, Av. Reyes Católicos 2, 28040 Madrid, Spain (e-mail: [email protected]). The authors declare no conflicts of interest. The American Journal of Dermatopathology: February 2018 - Volume 40 - Issue 2 - p 125-130 doi: 10.1097/DAD.0000000000000936 Buy Metrics 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. Copyright © 2017 Wolters Kluwer Health, Inc. All rights reserved.