Non-Asbestos-Related Malignant Peritoneal Mesothelioma: A Diagnostic Challenge in a Case of Unexplained Ascites

Our plain-English summary of Non-Asbestos-Related Malignant Peritoneal Mesothelioma: A Diagnostic Challenge in a Case of Unexplained Ascites, by M.A.F. Dar, N. Nasir, G. Mujtaba, et al (Curēus, 2025).

The study

• Authors: M.A.F. Dar, N. Nasir, G. Mujtaba, M. Afzal
• Journal: Curēus
• Published: 2025;17(10):e95421
• Type of article: Case report
• Read it: PubMed · Publisher · Free full text

Abstract

Malignant peritoneal mesothelioma (MPM) is a rare and aggressive malignancy arising from mesothelial cells of the peritoneum. It is most frequently linked to asbestos exposure, although up to half of cases occur without such history. Because of its vague and non-specific presentation, diagnosis is often delayed; cytology is frequently non-diagnostic, and histological confirmation with immunohistochemistry is required. Prognosis remains poor, although advances in cytoreductive surgery and intraperitoneal chemotherapy have improved outcomes in selected patients. We describe a man in his late 60s with no history of asbestos exposure who presented with progressive abdominal distension over 18 months. He underwent repeated paracenteses with negative cytology and multiple imaging studies, initially attributed to an intraductal papillary mucinous neoplasm (IPMN) under surveillance. Subsequent computed tomography (CT) demonstrated extensive peritoneal disease with omental caking and splenic lesions. Omental biopsy confirmed epithelioid-type MPM with BRCA1-associated protein 1 (BAP1) loss on immunohistochemistry. Given advanced disease and poor performance status, the patient was deemed unsuitable for surgery or chemotherapy and was managed with best supportive palliative care. This case highlights the diagnostic challenges of MPM, particularly in the absence of asbestos exposure and in the presence of coexistent pathology, and underscores the importance of early histological evaluation in patients with unexplained recurrent ascites.

Copyright © 2025, Dar et al.

In plain English

This case report, by doctors at the Royal Oldham Hospital in Oldham, UK, described one 69-year-old man with malignant peritoneal mesothelioma, a cancer of the abdominal lining. He had no occupational asbestos exposure, having worked in information technology; the article did not describe any other exposure history. Over 18 months he developed progressive abdominal swelling from fluid (ascites), with poor appetite, weight loss and tiredness. The fluid was at first thought to be related to a pancreatic cyst (IPMN) under surveillance. Fluid tests suggested a cause other than portal hypertension, possibly cancer, but repeated samples gave no diagnosis. A later CT scan showed extensive disease in the abdominal lining, deposits in a groin hernia and new spleen lesions. A chest CT showed no pleural disease. A biopsy confirmed epithelioid malignant mesothelioma with loss of the BAP1 protein. He was judged unsuitable for chemotherapy, and palliative care was recommended. The authors concluded that tissue examination should come early when fluid tests are inconclusive. A single case shows what happened to one patient, not how often this occurs.

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 (single patient)
• Who was studied: One 69-year-old man with hypertension and diabetes who was under surveillance for an intraductal papillary mucinous neoplasm (IPMN). The authors are from the Royal Oldham Hospital, Oldham, UK. The article gives no dates for the case.
• Exposure: No occupational asbestos exposure. He worked in the information technology sector. No fiber types or other exposures are described for the patient.
• Main results:
  • Progressive abdominal distension over 18 months, with longstanding ascites of uncertain origin.
  • Serum-ascites albumin gradient of 4 (serum albumin 23 g/L, ascitic albumin 19 g/L), which the authors read as suggesting a non-portal hypertensive, possibly malignant, cause.
  • Repeated ascitic fluid testing (cytology, culture, tuberculosis) did not establish a diagnosis.
  • CT of the abdomen and pelvis showed extensive peritoneal disease with omental caking, right inguinal hernia deposits and new splenic lesions.
  • CT of the chest showed lymph node enlargement but no pleural disease.
  • Tumour cells stained positive for the mesothelial markers calretinin, CK5/6, WT1 and D2-40. They were negative for the epithelial markers CEA and Ber-EP4, which excluded adenocarcinoma.
  • The omental biopsy was diagnosed as malignant mesothelioma of epithelioid type, with loss of BAP1.
  • Because of disease progression and declining performance status, the patient was deemed unsuitable for chemotherapy, and best supportive palliative care was recommended.
• The authors' conclusion: The authors concluded that the case underscores the importance of early histopathological evaluation when ascitic fluid cytology is inconclusive. They also stated that histology with immunohistochemistry remains the gold standard for diagnosis.

Topics

Medical terms in this study, explained in our Lexicon: Peritoneal Mesothelioma, Ascites, Mesothelial Cells, Peritoneum, Asbestos Exposure, Cytology, Immunohistochemistry, Prognosis.

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