Controversies in DermatopathologyKeratoacanthoma: Update on the DebateNirenberg, Alexander MBBS, BSc*; Steinman, Howard MD†,‡; Dixon, Anthony PhD, MBBS*,§Author Information *Australasian College of Cutaneous Oncology, Docklands, VIC, Australia; †Campbell University School of Osteopathic Medicine, Lillington, NC; ‡US Dermatology Partners, Grapevine, TX; and §American Osteopathic College of Dermatology, Kirskville, MO. Correspondence: Alexander Nirenberg, MBBS, BSc, Australasian College of Cutaneous Oncology, 10 Warwick Road, Pascoe Vale, Victoria 3044, Australia (e-mail: [email protected]). The authors declare no conflicts of interest. The American Journal of Dermatopathology: April 2021 - Volume 43 - Issue 4 - p 305-307 doi: 10.1097/DAD.0000000000001872 Buy Metrics Abstract Keratoacanthoma (KA) is a cutaneous tumor with a biphasic pattern of growth. A rapidly growing phase is usually followed by involution. KA occurs on sun-damaged skin. There are many listed causative associations, which include some therapeutic agents. Debate continues as to whether KA is a variant of squamous carcinoma (SCC) or a separate entity. Reporting of KA versus SCC is markedly inconsistent. Reasons for inconsistency include overlapping microscopic criteria, variants of KA with more aggressive features, and possibly medicolegal concerns. Genetic studies have shown some differences between the 2 entities. Activation of apoptotic pathways has been demonstrated in KA. Genetic studies have shown a possible role of human polyomavirus 6 in the pathogenesis of at least some KAs. Given that some cases of KA have components that behave as conventional SCCs, KA can be considered as a low-grade variant of SCC with some genetic differences. Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.