{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,8]],"date-time":"2026-09-08T14:30:28Z","timestamp":1788877828837,"version":"build-2803163510"},"reference-count":11,"publisher":"Ovid Technologies (Wolters Kluwer Health)","issue":"4","content-domain":{"domain":["lww.com","ovid.com"],"crossmark-restriction":true},"short-container-title":[],"published-print":{"date-parts":[[2024,4]]},"abstract":"<jats:p>A well-differentiated papillary mesothelial tumor (WDPMT) and malignant mesothelioma are 2 well-recognized entities arising from the testis tunica vaginalis. Another mesothelial lesion exclusively seen at this site is mesothelioma of uncertain malignant potential (MUMP)\u2014a lesion reminiscent of WDPMT yet demonstrating variable proportions of more complex architectural patterns that could be confused with invasion. MUMP was first described in 2010 with a total of 11 cases reported to date. Herein, we describe 19 additional patients who underwent hydrocelectomy, excision, and\/or orchiectomy. Novel morphologic patterns found in addition to the 2010 series include spindle cells, keloidal-type collagen, and multicystic architecture lined by bland mesothelial cells. Clinical follow-up in 9 patients for more than 1 year (1.5 to 22.5\u00a0y, median 4.5\u00a0y) revealed no evidence of disease recurrence or metastases. Despite greater architectural complexity, MUMP has (1) bland cytology; (2) merging in with WDPMT areas; (3) low mitotic rate and Ki-67 nuclear labeling index; (4) retention of MTAP and BAP1 expression; and (5) benign clinical follow-up. If these cases were malignant mesotheliomas, one would have expected at least some of the patients to demonstrate disease recurrence\/progression without adjuvant therapy within the available follow-up time, particularly with limited resection in most patients. Thus, we propose that \u201cmesothelioma of uncertain malignant potential\u201d be renamed as \u201ccomplex mesothelial tumor of the tunica vaginalis.\u201d Using the term \u201ccomplex\u201d draws a contrast with the simple cuboidal lining and simple papillary architecture seen in WDPMT. Also, labeling the lesion as \u201ctumor\u201d removes the stigmata of \u201cuncertain malignant potential\u201d and \u201cmesothelioma\u201d that are alarming to patients and clinicians, and potentially could unduly lead to more extensive surgery in an attempt at \u201ccomplete\u201d resection. At the same time, not definitively labeling the lesion as benign allows recommendations for follow-up.<\/jats:p>","DOI":"10.1097\/pas.0000000000002185","type":"journal-article","created":{"date-parts":[[2024,1,25]],"date-time":"2024-01-25T16:04:37Z","timestamp":1706198677000},"page":"387-394","update-policy":"https:\/\/doi.org\/10.1097\/lww.0000000000001000","source":"Crossref","is-referenced-by-count":7,"title":["Mesothelioma of Uncertain Malignant Potential (MUMP) of the Tunica Vaginalis"],"prefix":"10.1097","volume":"48","author":[{"given":"Chien-Kuang C.","family":"Ding","sequence":"first","affiliation":[{"name":"Departments of Pathology"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jason","family":"Van Roo","sequence":"additional","affiliation":[{"name":"Departments of Pathology"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Oleksandr N.","family":"Kryvenko","sequence":"additional","affiliation":[{"name":"Department of Pathology, Desai Sethi Urology Institute, Department of Radiation Oncology, Sylvester Comprehensive Cancer Center, University of Miami Miller School of Medicine, Miami, FL"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Huihui","family":"Ye","sequence":"additional","affiliation":[{"name":"Department of Pathology & Laboratory Medicine, University of California, Los Angeles, CA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jesse K.","family":"McKenney","sequence":"additional","affiliation":[{"name":"Department of Anatomic Pathology, Cleveland Clinic, Cleveland, OH"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jonathan I.","family":"Epstein","sequence":"additional","affiliation":[{"name":"Urology"},{"name":"Oncology, Johns Hopkins University School of Medicine, Baltimore, MD"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"276","published-online":{"date-parts":[[2024,1,25]]},"reference":[{"key":"R1-20250608","doi-asserted-by":"crossref","first-page":"990","DOI":"10.1097\/PAS.0000000000000200","article-title":"Well-differentiated papillary mesothelioma with invasive foci","volume":"38","author":"Churg","year":"2014","journal-title":"Am J Surg Pathol"},{"key":"R2-20250608","doi-asserted-by":"crossref","first-page":"65","DOI":"10.1111\/his.14669","article-title":"Molecular and immunohistochemical characterisation of mesothelioma of the tunica vaginalis","volume":"81","author":"Anderson","year":"2022","journal-title":"Histopathology"},{"key":"R3-20250608","doi-asserted-by":"crossref","first-page":"259","DOI":"10.1097\/PAP.0000000000000371","article-title":"Malignant mesothelioma of Tunica Vaginalis testis: update for 2022","volume":"30","author":"Iczkowski","year":"2022","journal-title":"Adv Anat 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Pathol"},{"key":"R11-20250608","doi-asserted-by":"crossref","first-page":"1032","DOI":"10.1111\/his.14324","article-title":"Correlation of methylthioadenosine phosphorylase (MTAP) protein expression with MTAP and CDKN2A copy number in malignant pleural mesothelioma","volume":"78","author":"Chapel","year":"2021","journal-title":"Histopathology"},{"key":"R12-20250608","doi-asserted-by":"crossref","first-page":"245","DOI":"10.1038\/s41379-019-0310-0","article-title":"MTAP immunohistochemistry is an accurate and reproducible surrogate for CDKN2A fluorescence in situ hybridization in diagnosis of malignant pleural mesothelioma","volume":"33","author":"Chapel","year":"2020","journal-title":"Mod Pathol"}],"container-title":["American Journal of Surgical 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