Well-differentiated papillary mesothelial tumor of the peritoneum in a young woman: A case report with molecular insights

Our plain-English summary of Well-differentiated papillary mesothelial tumor of the peritoneum in a young woman: A case report with molecular insights, by R. Xu, S. Xu, X. Wang, et al (Medicine, 2025).

The study

• Authors: R. Xu, S. Xu, X. Wang, Y. Ren, L. Su, J. Su
• Journal: Medicine
• Published: 2025;104(48):e46241
• Type of article: Case report
• Read it: PubMed · Publisher · Free full text

Abstract

Rationale: Well-differentiated papillary mesothelial tumor (WDPMT) is an uncommon, slow-growing neoplasm that is often an incidental finding in the peritoneum of women of reproductive age. It can be misdiagnosed as malignant mesothelioma on routine histology, potentially leading to unnecessary aggressive therapy. The role of modern molecular techniques in resolving this diagnostic dilemma and guiding conservative management warrants emphasis.

Patient Concerns: A 32-year-old woman presented with vague abdominal discomfort. Imaging revealed bilateral ovarian cysts and significant pelvic free fluid.

Diagnoses: Laparoscopy identified multiple small peritoneal nodules. Initial frozen-section histology suggested malignant mesothelioma. Definitive diagnosis of WDPMT was established through comprehensive immunohistochemistry (retained BAP1 expression) and next-generation sequencing, which revealed a low tumor mutational burden and a pathogenic GPR124 mutation. This genetic profile distinct from malignant mesothelioma.

Interventions: After definitive diagnosis and thorough counseling, the patient opted against cytoreductive surgery or systemic therapy. A strategy of active surveillance with serial imaging and tumor marker assessment was implemented.

Outcomes: The patient remained asymptomatic with no evidence of disease recurrence or progression 24 months after diagnosis.

Lessons: This case highlights that a definitive distinction between WDPMT and malignant mesothelioma is paramount, as it dictates a radically different management strategy. Integration of immunohistochemistry (particularly BAP1) and molecular profiling is essential for accurate diagnosis and can prevent overtreatment. For appropriately selected patients with WDPMT, conservative management with active surveillance represents a safe and effective approach, underscoring the value of precision medicine in guiding patient-centric care.

Copyright © 2025 the Author(s). Published by Wolters Kluwer Health, Inc.

In plain English

This article was a case report about one patient, a 32-year-old woman who had never given birth. She was admitted in October 2023 after routine ultrasound had found ovarian cysts and fluid in the pelvis. During laparoscopy, surgeons found many small nodules, 0.5 to 1.0 cm across, on the lining of the pelvis (the pelvic peritoneum). The first hospital's pathology report described the nodules as consistent with epithelioid malignant mesothelioma. An expert review at Peking University Third Hospital changed the diagnosis to well-differentiated papillary mesothelial tumor (WDPMT). That review used additional tissue stains, which showed retained BAP1, and genetic sequencing, which found a GPR124 mutation and a low tumor mutational burden. The ovarian cyst was also reclassified, as an endometriotic cyst. After counseling, she chose no further surgery or drug treatment and was monitored instead. About 20 months after diagnosis she had no symptoms and no sign of recurrence or progression. The authors concluded that molecular testing helps avoid overtreatment and that surveillance can be safe in properly diagnosed WDPMT. The article does not mention asbestos or any other exposure.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: case report (retrospective analysis of a single patient)
• Who was studied: One 32-year-old nulliparous woman, admitted October 9, 2023; the authors' hospitals are in Shijiazhuang, China
• Main results:
  • At laparoscopy, scattered nodules of 0.5 to 1.0 cm were found on the pelvic peritoneum of this patient. No disease was seen on the omentum, bowel, liver or diaphragm.
  • The first institution's final pathology of the peritoneal nodule was read as consistent with epithelioid malignant mesothelioma.
  • Expert review established the diagnosis as WDPMT. This review added further stains (including BAP1+ and MTAP+) and next-generation sequencing, which found a GPR124 mutation (variant allele frequency 2.1%) and a tumor mutational burden of 0 mut/Mb.
  • The ovarian cyst diagnosis was revised from mucinous cystadenoma to an endometriotic cyst.
  • After declining further surgery or adjuvant therapy, the patient was under surveillance. At about 20 months after diagnosis she had no symptoms and no evidence of recurrence or progression.
• The authors' conclusion: The authors concluded that conservative management and disease-free status at 20 months in this case show that surveillance can be a safe and effective strategy in properly diagnosed WDPMT. They also concluded that molecular diagnostics help avoid overtreatment.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Mesothelioma, Peritoneal mesothelioma.

Medical terms in this study, explained in our Lexicon: Well-Differentiated, Peritoneum, Neoplasm, Mesothelioma, Histology, Bilateral, Immunohistochemistry, BAP1.

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• Heterozygous loss of NF2 is an early molecular alteration in well-differentiated papillary mesothelioma of the peritoneum — H. Nemoto, G. Tate, et al. (2012)
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