RT Journal Article SR Electronic T1 Cutaneous Epithelial Lesions Induced by N-Methyl-N-nitrosourea in Male Sprague-Dawley Rats: A Possible Animal Model for Human Keratoacanthoma JF Anticancer Research JO Anticancer Res FD International Institute of Anticancer Research SP 111 OP 120 VO 36 IS 1 A1 MICHIKO YUKI A1 KATSUHIKO YOSHIZAWA A1 YUKO EMOTO A1 TAKASHI YURI A1 YUICHI KINOSHITA A1 AIRO TSUBURA A1 ICHIRO KUROKAWA YR 2016 UL http://ar.iiarjournals.org/content/36/1/111.abstract AB A single intraperitoneal injection of 50 or 75 mg/kg N-methyl-N-nitrosourea in male Sprague-Dawley rats at 4 weeks of age, dose-dependently resulted in cutaneous epithelial cysts and tumors of pilosebaceous origin. Cysts were composed of epidermal cysts or mixed epidermal and inner root sheath hybrid cysts. The majority of induced tumors were keratoacanthomas. A few tumors were trichofolliculomas, trichoblastomas, pilomatricomas, or sebaceous adenomas. All tumors were benign pilosebaceous tumors. Keratoacanthomas were crater-shaped tumors with thick infoldings of epithelium containing keratohyalin granules (epidermal lip) that abruptly changed to epithelium containing trichohyalin granules. The morphological similarity and resemblance of keratin 1, 10, and 14 profiles, and p63 and β-catenin expression between mixed epidermal and inner root sheath hybrid cysts and keratoacanthomas suggests that hybrid cysts progressed to keratoacanthomas, and the cells from infundibular cells to inner root sheath cells of the pilar segment seem to be the origin of rat keratoacanthomas. Immunohistochemical localization of keratins 1, 10 and 14, p63, and β-catenin in trichofolliculoma, trichoblastoma, and pilomatricoma, as well as keratoacanthoma, may indicate tumor histogenesis.