Malignant mesothelioma in rare sites: two case reports

Our plain-English summary of Malignant mesothelioma in rare sites: two case reports, by Q. Du, J. Guo, Z. Zhu, et al (Frontiers in Oncology, 2025).

The study

• Authors: Q. Du, J. Guo, Z. Zhu, Y. Zhang, H. Cui, Z. Xu, R. Yang, W. Liang
• Journal: Frontiers in Oncology
• Published: 2025;15:1698949
• Type of article: Case report
• Read it: PubMed · Publisher · Free full text

Abstract

Mesothelioma is a rare tumor originating from mesothelial cells in the pleura or other sites. Malignant pleural mesothelioma (MPM) is the most common aggressive type of mesothelioma (accounting for 81%) and carries a poor prognosis (median OS: 1 year). Diagnosing diverse histologic types is challenging. We report two cases: a 72-year-old female with peritoneal mesothelioma demonstrated a remarkable response, with the lesion shrinking from 150×160mm to radiologically undetectable after chemo-immunotherapy, resulting in a sustained complete response. Conversely, a 66-year-old male with MPM exhibited primary platinum resistance, progressing after first-line pemetrexed/lobaplatin and subsequent second-line chemotherapy. Peritoneal mesothelioma responded better to immuno-chemotherapy, while MPM showed platinum resistance. These contrasting disparate outcomes underscore that precise pathology and individualized treatment based on anatomic site are crucial, suggesting that malignant pleural and peritoneal mesothelioma may represent distinct clinical entities.

Copyright © 2025 Du, Guo, Zhu, Zhang, Cui, Xu, Yang and Liang.

In plain English

This article reported two patients with mesothelioma treated at a hospital in Harbin, China. The first, a 72-year-old woman, had peritoneal mesothelioma confirmed by biopsy staining. From May 2024 she received six 21-day cycles of pemetrexed, cisplatin and the immunotherapy drug toripalimab, then toripalimab alone. Her pelvic mass measured 150 × 160 mm at the start and showed a partial response after six cycles. By July 2025 it could no longer be seen on imaging, which the authors classed as a complete response. Her blood marker CA15-3 fell from 41.8 to 10.0 U/mL. The second, a 66-year-old man with pleural mesothelioma diagnosed in October 2022, had stable disease after eight cycles of pemetrexed and lobaplatin, then pemetrexed alone for 13 cycles because of side effects. His disease then progressed, which the authors called primary platinum resistance, and it progressed further on docetaxel and cisplatin. The article did not describe asbestos exposure for either patient. The authors concluded that anatomical site should be a key factor in treatment planning, and that larger prospective trials are needed.

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 of two patients
• Who was studied: Two patients at the Second Affiliated Hospital of Harbin Medical University, China. The first was a 72-year-old woman with malignant peritoneal mesothelioma who presented in February 2024. The second was a 66-year-old man with malignant pleural mesothelioma: pleural effusion was found in May 2022 and he was diagnosed in October 2022.
• Exposure: Not reported. The article does not describe asbestos exposure, fiber types or occupation for either patient.
• Main results:
  • Peritoneal mesothelioma patient: after six cycles of pemetrexed, cisplatin and toripalimab ending in September 2024, she had a partial response, and maintenance toripalimab was started.
  • Peritoneal mesothelioma patient: the pelvic mass measured 150 × 160 mm at baseline in May 2024 with CA15-3 at 41.8 U/mL. After 3 cycles it measured 163 × 145 mm (stable disease). By July 2025 it was undetectable, CA15-3 was 10.0 U/mL, and the response was classed as complete.
  • Pleural mesothelioma patient: 8 cycles of pemetrexed and lobaplatin (January to June 2023) gave stable disease. Because of toxicity, treatment was reduced to pemetrexed alone for 13 cycles. The disease then progressed, which the authors described as primary platinum resistance.
  • Pleural mesothelioma patient: a new chest wall mass in May 2024 led to second-line docetaxel and cisplatin. Imaging later showed further progression, with increased right-sided pleural effusion and enlarged mediastinal lymph nodes.
• The authors' conclusion: The authors concluded that anatomical location should be a key factor in risk stratification and treatment planning. They said it warrants exploration whether peritoneal mesothelioma benefits more from immunochemotherapy while pleural mesothelioma needs early molecular subtyping. They added that such approaches are preliminary and need larger prospective trials.
• Limitations the authors state:
  • The retrospective design meant there were no standardized biomarker analyses: no tumor-infiltrating lymphocyte counts, no PD-L1 scoring and no next-generation sequencing.
  • Response was judged by conventional imaging and blood markers, without confirmatory biopsy or circulating tumor DNA testing.
  • Two cases are insufficient to establish a definitive treatment approach.

Topics

Medical terms in this study, explained in our Lexicon: Mesothelioma, Mesothelial Cells, Pleura, Pleural Mesothelioma, Prognosis, Peritoneal Mesothelioma, Immunotherapy, Pemetrexed (Alimta).

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