Malignant Mesothelioma Extending from Peritoneum to Pleura: A Diagnostic Challenge and Case Report

Our plain-English summary of Malignant Mesothelioma Extending from Peritoneum to Pleura: A Diagnostic Challenge and Case Report, by T.T. Phan, T.Q.H. Pham, V.D. Le, et al (Case Reports in Oncology, 2026).

The study

• Authors: T.T. Phan, T.Q.H. Pham, V.D. Le, T.L. Tran, V.C. Tran, N. Thị Hoa Mai, T.P. Phan, V.G. Vu
• Journal: Case Reports in Oncology
• Published: 2026;19(1):785-795
• Type of article: Case report
• Read it: PubMed · Publisher · Free full text

Abstract

Introduction: Sarcomatoid malignant peritoneal mesothelioma (SM-MPM) is an exceptionally rare and aggressive subtype of peritoneal mesothelioma, often presenting with nonspecific symptoms such as ascites. Due to its subtle clinical manifestations, diagnosis is frequently delayed, resulting in poor prognosis. Early and accurate identification is crucial for guiding appropriate therapeutic strategies.

Case Presentation: We report the case of a 52-year-old woman with no history of smoking, alcohol use, or asbestos exposure, who previously underwent subtotal hysterectomy for uterine fibroids in 2017. Ten months prior to admission, she developed progressive abdominal distension, fatigue, and ascites, accompanied by elevated CA-125 levels. Initial symptomatic improvement was achieved with diuretics, but no definitive diagnosis was established. Eight months later, she was readmitted with recurrent ascites, chest tightness, and dyspnea. Imaging revealed right pleural effusion, pneumothorax, and peritoneal thickening. Pleuroscopic biopsy showed reactive mesothelial proliferation. One month into hospitalization, rapid re-accumulation of ascitic fluid prompted repeat imaging, which demonstrated irregular peritoneal thickening and nodularity. Laparoscopic peritoneal biopsy with immunohistochemistry confirmed the diagnosis of SM-MPM. The disease was staged as T3N0M1 based on the Peritoneal Cancer Index (PCI), indicating advanced disease with poor prognosis. The patient was referred to a specialized oncology center for further management.

Conclusions: This case underscores the diagnostic challenges of SM-MPM, particularly in patients presenting with recurrent unexplained ascites and multiple serous effusions. It highlights the importance of maintaining a high index of suspicion and the pivotal role of laparoscopy, immunohistochemistry, and multidisciplinary collaboration in achieving timely diagnosis and optimizing patient outcomes.

© 2026 The Author(s). Published by S. Karger AG, Basel.

In plain English

This case report from Bach Mai Hospital in Hanoi, Vietnam, described one 52-year-old woman with sarcomatoid malignant peritoneal mesothelioma (SM-MPM), a rare cancer of the abdominal lining. The article reported no history of alcohol use, smoking, or occupational asbestos exposure. Abdominal swelling and fluid (ascites) began about 10 months before presentation. At her first admission, in October 2024, the blood marker CA-125 was 258 U/mL, above the normal range. Diuretics gave temporary relief but no diagnosis. Eight months later she returned with fluid and air around the right lung. A pleural biopsy then showed only reactive mesothelial hyperplasia and did not show mesothelioma. After the abdominal fluid built up quickly, biopsy of peritoneal nodules taken during laparoscopy confirmed SM-MPM. A later review of the pleural slides raised concern for epithelioid mesothelioma there. The disease was staged T3N0M1, with a Peritoneal Cancer Index score of 26. After four cycles of doxorubicin and ifosfamide, the authors wrote that her responses suggested partial remission. She had grade 3 neutropenia, a low neutrophil count, after the third cycle. The authors concluded that this disease should be suspected in recurrent unexplained ascites.

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 (a single patient)
• Who was studied: One 52-year-old woman with a previous subtotal hysterectomy for uterine fibroids (2017), treated at Bach Mai Hospital, Hanoi, Vietnam, first admitted October 2024
• Exposure: No asbestos exposure was studied. The patient was reported to have no history of alcohol consumption, smoking, or occupational asbestos exposure.
• Main results:
  • At the patient's first workup, her serum CA-125 was elevated at 258 U/mL (reference range 0 to 35 U/mL)
  • The patient's initial pleural biopsy showed reactive mesothelial hyperplasia and did not show malignant pleural mesothelioma at that time
  • Biopsy of multiple peritoneal nodules taken during diagnostic laparoscopy confirmed sarcomatoid malignant peritoneal mesothelioma in this patient. The biopsy was examined by histopathology and immunohistochemistry.
  • On later review, the patient's pleural biopsy slides showed areas suspicious for stromal invasion. This raised concern for epithelioid mesothelioma in the pleural specimen.
  • The patient's disease was staged T3N0M1 with a Peritoneal Cancer Index score of 26, which the authors described as consistent with advanced disease
  • After four cycles of doxorubicin plus ifosfamide (AI regimen), the authors wrote that the patient's clinical and radiologic responses suggested partial remission
  • The patient developed grade 3 neutropenia (neutrophils 0.78 G/L) after the third chemotherapy cycle
  • The authors noted that early imaging had already shown subtle abnormalities: minimal ascites, diffuse peritoneal thickening and raised CA-125. These were not followed up with diagnostic laparoscopy at the time, which contributed to the diagnostic delay.
• The authors' conclusion: The authors concluded that clinicians should maintain a high index of suspicion for peritoneal mesothelioma in patients with recurrent unexplained ascites or effusions in more than one body cavity. They stressed early diagnostic laparoscopy, immunohistochemistry and multidisciplinary collaboration.

Topics

Medical terms in this study, explained in our Lexicon: Mesothelioma, Peritoneum, Pleura, Sarcomatoid, Peritoneal Mesothelioma, Ascites, Prognosis, Asbestos Exposure.

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• Lung cancer and mesothelioma in the pleura and peritoneum among Swedish insulation workers — B. Järvholm, A. Sandén (1998)
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