Original StudySebaceous Tumors of the Skin: A Study of 145 Lesions From 136 Patients Correlating Pathologic Features and DNA Mismatch Repair Staining PatternKonstantinova, Anastasia M. MD, PhD*,†,‡; Kastnerova, Liubov MD, PhD§; Michal, Michal MD§,¶; Kolm, Isabel MD‖; Kazakov, Dmitry V. MD, PhD§,¶,‖Author Information *Department of Pathology, Clinical Research and Practical Center for Specialized Oncological Care, Saint-Petersburg, Russia; †Department of Pathology, Medical Faculty, Saint-Petersburg State University, Saint Petersburg, Russia; ‡Department of Pathology, Saint-Petersburg Medico-Social Institute, Saint Petersburg, Russia; §Sikl's Department of Pathology, Medical Faculty in Pilsen, Charles University in Prague, Pilsen, Czech Republic; ¶Bioptical Laboratory, Pilsen, Czech Republic; and ‖Department of Dermatology, University Hospital, Zurich, Switzerland. Correspondence: Dmitry V. Kazakov, MD, PhD, Sikl's Department of Pathology, Charles University Medical Faculty Hospital, Alej Svobody 80, 304 60 Pilsen, Czech Republic (e-mail: [email protected]). The authors declare no conflicts of interest. The American Journal of Dermatopathology: March 2021 - Volume 43 - Issue 3 - p 174-181 doi: 10.1097/DAD.0000000000001691 Buy Metrics Abstract Sebaceous neoplasms occur sporadically or in the setting of Muir–Torre syndrome. The data regarding the correlation of pathologic features and DNA mismatch repair (MMR) staining pattern in sebaceous tumors of the skin are very scanty and based on relatively small series of patients. The goal of this study was to correlate MMR staining pattern with selected morphological features in a series of 145 sebaceous neoplasms (sebaceous adenoma, sebaceoma, and extraocular sebaceous carcinoma) from 136 patients. Cystic change, intratumoral mucin deposits, squamous metaplasia in the absence of keratoacanthoma-like changes, ulceration, intratumoral and peritumoral lymphocytes (in cases without epidermal ulceration), and intertumoral heterogeneity proved to be significantly associated with MMR deficiency. Identification of any of these changes, alone or in combination, should prompt further investigation of the patient to exclude Muir–Torre Syndrome. Our study also confirms the previously published observation that the diagnosis and tumor location are significantly associated with MMR deficiency. Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.