Localized peritoneal epithelioid clear cell subtype mesothelioma: a case report and literature review

Our plain-English summary of Localized peritoneal epithelioid clear cell subtype mesothelioma: a case report and literature review, by B. Huang, H. Liu, H. Zhou (Frontiers in Oncology, 2026).

The study

• Authors: B. Huang, H. Liu, H. Zhou
• Journal: Frontiers in Oncology
• Published: 2026;16:1790964
• Type of article: Case report
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Epithelioid mesothelioma with a clear cell morphology is rare and has only been described in a few case reports. The diagnosis of epithelioid clear cell mesothelioma is challenging and often requires extensive immunohistochemical staining. Here, we report a case of epithelioid mesothelioma, clear cell variant, occurring in the peritoneum of a 76-year-old male. Computed Tomography(CT)imaging revealed a localized irregular intra-abdominal mass measuring approximately 6.0×5.0cm. Combined with histomorphology and immunophenotype analysis, the patient was diagnosed with localized epithelioid clear cell mesothelioma. There was no recurrence or metastasis after 24 months of follow-up. This case enriches the clinical and molecular data of localized peritoneal epithelioid clear cell mesothelioma, and provides insights into its diagnosis, differential diagnosis, and treatment.

Copyright © 2026 Huang, Liu and Zhou.

In plain English

This was a case report about one patient: a 76-year-old man admitted to a hospital in Hangzhou, China, with upper abdominal bloating lasting more than 10 days. He had no history of occupational exposure such as asbestos exposure. A CT scan showed an irregular mass of about 6.0 by 5.0 cm in the right upper abdomen, first suspected to be a gastrointestinal stromal tumor. Surgeons removed part of the colon with the mass, which measured 7.0 by 4.5 by 4.0 cm on the colon's outer surface. The tumor consisted of epithelioid cells with clear cytoplasm and extensive necrosis. Stains were positive for calretinin, cytokeratin and desmin, and negative for BAP1, CD117 and DOG1. Genetic testing found ALK, MSH2 and ATM mutations whose clinical significance, the authors said, remains unknown. The diagnosis was localized peritoneal epithelioid clear cell subtype mesothelioma. He had no radiotherapy or chemotherapy and stayed disease-free over 24 months of follow-up. The authors concluded the case highlights the curative potential of surgery for localized lesions, noting that a single case and short follow-up limit the findings.

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 76-year-old man admitted to The First People's Hospital of Xiaoshan District, Hangzhou, China, with upper abdominal distension lasting more than 10 days
• Exposure: No asbestos exposure was reported. The patient had no history of occupational exposure such as asbestos exposure.
• Main results:
  • Contrast-enhanced CT showed an irregular mass of approximately 6.0×5.0 cm in the right upper abdomen, first suggesting a possible gastrointestinal stromal tumor (GIST)
  • In the surgical specimen, an irregular nodular mass measuring 7.0×4.5×4.0 cm was found on the serosal (outer) surface of the colon
  • Under the microscope the tumor showed epithelioid cells with moderate atypia and clear cytoplasm, and multiple areas of extensive necrosis
  • Immunohistochemistry was positive for cytokeratin (CK), calretinin and desmin; WT-1 was weakly positive; BAP1 was negative
  • BAP1 staining was negative in the tumor cells
  • CD117 and DOG1 were negative, which the authors said ruled out GIST and pointed to mesothelioma
  • The Ki-67 proliferation index was 20%
  • Next-generation sequencing found an ALK exon 20 mutation with a variant allele frequency of 8.77%
  • Sequencing also found an MSH2 exon 12 mutation (frequency 3.25%) and an ATM exon 18 mutation (frequency 5.23%); the clinical significance of these mutations was stated to be unknown
  • Microsatellite instability analysis showed MSI-L (microsatellite instability-low), which the authors said suggests potential insensitivity to immunotherapy
  • The tumor was surgically removed with no postoperative radiotherapy or chemotherapy, and the patient remained disease-free during 24 months of follow-up
• The authors' conclusion: The authors concluded that the case confirmed a diagnosis of a rare localized epithelioid clear cell subtype of peritoneal mesothelioma and highlights the curative potential of surgical resection in localized lesions, and that the molecular variations found need further research for validation
• Limitations the authors state:
  • It is a single case report, and the clinical significance of the molecular mutations needs to be verified by large studies
  • Follow-up was short, and the long-term risk of recurrence and metastasis still needs further follow-up

Topics

Medical terms in this study, explained in our Lexicon: Epithelioid, Mesothelioma, Immunohistochemistry, Peritoneum, Metastasis, Differential Diagnosis.

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