Extraordinary Case ReportMetastatic Prostatic Adenocarcinoma in Patient With Muir–Torre Syndrome Misdiagnosed as Metastatic Sebaceous Carcinoma: Case Report and Systematic Literature ReviewCattelan, Leila BSc*; Abi-Rafeh, Jad HBSc, MSc*; Brimo, Fadi MD, FRSC†; Kazan, Roy MD, PhD‡; Redpath, Margaret MD, PhD, FRCSC§; Chergui, May MD, FRCPC†Author Information *Faculty of Medicine, McGill University, Montreal, Québec, Canada; †Department of Pathology, McGill University Health Centre, Montreal, Québec, Canada; ‡Division of Plastic and Reconstructive Surgery & Division of Experiential Surgery, Department of Surgery, McGill University Health Centre, Montreal, Québec, Canada; and §Department of Pathology, Jewish General Hospital, Montreal, Québec, Canada. Correspondence: May Chergui, MD, FRCPC, Department of Pathology and Division of Dermatopathology, McGill University, 1001 Decarie Boulevard, Montreal, QC H4A 3J1, Canada (e-mail: firstname.lastname@example.org). The authors declare no conflicts of interest. L. Cattelan and J. Abi-Rafeh authors share first authorship of this work. The case report which forms part of this work was conducted with informed written consent from the patient. The conduct of this project was also submitted to our institutional Research Ethics Board (REB) which determined that this work was exempt from REB review according to institutional policies. The American Journal of Dermatopathology: September 2020 - Volume 42 - Issue 9 - p 700-705 doi: 10.1097/DAD.0000000000001633 Buy Metrics Abstract Muir–Torre syndrome (MTS) is a rare autosomal dominant condition characterized by the presence of at least one cutaneous sebaceous tumor and one visceral malignancy, arising mostly from the gastrointestinal tract. We present the case of a 63-year-old man with several cutaneous and visceral neoplasias in the context of MTS, and a pelvic lymph node lesion diagnosed initially as metastatic sebaceous carcinoma, but later identified as metastasis from a newly diagnosed prostatic adenocarcinoma. Histological similarities between these 2 lesions are discussed. A systematic literature review was conducted evaluating all published cases of patients with MTS in which metastases were reported. Eighteen articles were included in the final synthesis, representing 20 patients with a total of 26 metastases. Seventeen patients (85%) exhibited metastases originating from MTS-related neoplasms, whereas only 2 patients (11%) exhibited metastases from concomitant malignancies. Of the 85% of patients with metastases from MTS-related malignancies, most originated from noncutaneous sources (78% from visceral neoplasms and 22% from sebaceous carcinomas). When stratifying according to metastases, 23 cases (88%) originated from MTS-related lesions, whereas only 3 (12%) originated from unrelated malignancies. Our findings thus demonstrate that most metastases found in MTS patients (88%) do indeed originate from MTS-related neoplasms. Nevertheless, it remains imperative that a broad differential diagnosis is maintained when assessing a novel lesion, to avoid misdiagnoses, as in the present case, with significant therapeutic and prognostic implications. Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.