Review ArticlesSWI/SNF-deficient Sinonasal CarcinomasAgaimy, Abbas MD Author Information Institute of Pathology, Friedrich-Alexander-University Erlangen-Nürnberg, University Hospital, Erlangen, Germany The authors have no funding or conflicts of interest to disclose. Reprints: Abbas Agaimy, MD, Pathologisches Institut, Universitätsklinikum Erlangen, Krankenhausstrasse 8-10, Erlangen 91054, Germany (e-mail: [email protected]). Advances In Anatomic Pathology 30(2):p 95-103, March 2023. | DOI: 10.1097/PAP.0000000000000372 Buy Metrics Abstract The classification of poorly differentiated sinonasal carcinomas and their nonepithelial mimics has experienced tremendous developments during the last 2 decades. These recent developments paved the way for an increasingly adopted approach to a molecular-based or etiology-based refined classification of the many carcinoma variants that have been historically lumped into the sinonasal undifferentiated carcinoma category. Among these new achievements, recognition of carcinoma subtypes driven by defects in the Switch/Sucrose nonfermentable (SWI/SNF) chromatin remodeling complex represents a major highlight. This resulted in a new definition of 4 sinonasal entities driven solely or predominantly by Switch/Sucrose nonfermentable complex deficiency: (1) SMARCB1(INI1)-deficient sinonasal carcinoma (lacking gland formation and frequently displaying a non-descript basaloid, and less frequently eosinophilic/oncocytoid morphology, but no features of other definable subtypes), (2) SMARCB1-deficient sinonasal adenocarcinoma (with unequivocal glands or yolk sac-like pattern), (3) SMARCA4-deficient undifferentiated (sinonasal undifferentiated carcinoma-like) carcinoma (lacking glandular or squamous immunophenotypes), and (4) SMARCA4-deficient subset (~80%) of sinonasal teratocarcinosarcoma. Fortunately, diagnostic loss of all these proteins can be detected by routine immunohistochemistry, so that genetic testing is not mandatory in routine practice. This review summarizes the main demographic, clinicopathological, and molecular features of these new entities. Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.