Sarcomatoid Mesothelioma Revealed After Treatment for Tuberculous Pleurisy: A Case Report

Our plain-English summary of Sarcomatoid Mesothelioma Revealed After Treatment for Tuberculous Pleurisy: A Case Report, by D. Nagayama, K. Yokoo, Y. Yabushita, et al (Respirology Case Reports, 2026).

The study

• Authors: D. Nagayama, K. Yokoo, Y. Yabushita, M. Sekikawa, M. Abe, H. Kato, A. Takayanagi, B. Takahashi, M. Kato-Shinomiya, S. Ota, G. Yamada, K. Hiroshima, H. Chiba
• Journal: Respirology Case Reports
• Published: 2026;14(9):e70734
• Read it: PubMed · Publisher · Free full text

Abstract

Differentiating tuberculous (TB) pleurisy from malignant pleural mesothelioma is challenging due to similar clinical presentations. We report an 83-year-old man with sarcomatoid mesothelioma initially treated for TB pleurisy. He presented with lymphocyte-predominant exudative pleural effusion and a positive Interferon-Gamma Release Assay. Thoracoscopy revealed purulent effusion, but biopsies were non-diagnostic. Despite empiric anti-tuberculosis therapy, the effusion persisted. A subsequent surgical biopsy showed fibrosis and scattered spindle cells. However, 2 months later, a rapidly growing chest wall mass with bone invasion appeared. A CT-guided percutaneous biopsy showed proliferation of atypical spindle cells and fluorescence in situ hybridization (FISH) analysis allowed for the diagnosis of sarcomatoid mesothelioma. This case highlights the aggressive nature of sarcomatoid mesothelioma and its diagnostic difficulty. For treatment-refractory pleurisy, clinicians must maintain high suspicion, ensuring vigilant follow-up and prompt repeat biopsies despite negative initial results, while consulting pathologists to consider additional FISH testing.

© 2026 The Author(s). Respirology Case Reports published by John Wiley & Sons Australia, Ltd on behalf of The Asian Pacific Society of Respirology.

In plain English

This case report, from Teine Keijinkai Hospital in Sapporo, Japan, described an elderly man whose sarcomatoid mesothelioma of the pleura was first treated as tuberculous pleurisy (tuberculosis affecting the lining of the lung). A positive tuberculosis blood test (IGRA) and the type of fluid around the lung supported the first diagnosis, and anti-tuberculosis drugs were started in January 2025. The fluid did not go away. After 4 months of treatment, a thoracoscopic biopsy showed fibrous thickening of the pleura with no signs of tuberculosis, and cultures were negative. Two months after that surgery, a CT scan showed a new mass invading the right 8th rib. A needle biopsy of the mass, together with a genetic test (FISH) showing a homozygous deletion of CDKN2A (p16), confirmed sarcomatoid mesothelioma. The patient died two months after the diagnosis, receiving best supportive care. The authors concluded that patients who respond poorly to treatment for presumed tuberculous pleurisy need prompt repeat biopsies, and that access to FISH testing needs to expand. The article did not discuss asbestos 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
• Who was studied: One elderly man, referred to Teine Keijinkai Hospital, Sapporo, Japan, in April 2025
• Main results:
  • A positive IGRA and lymphocyte-predominant effusion supported an initial diagnosis of tuberculous pleurisy. Anti-tuberculosis drugs (isoniazid, rifampicin, ethambutol, pyrazinamide) were started in January 2025.
  • The pleural effusion persisted despite the anti-tuberculosis treatment.
  • A thoracoscopic biopsy after 4 months of treatment showed fibrous pleural thickening without granulomatous inflammation or acid-fast bacilli. Tissue cultures were negative.
  • In August 2025, a CT scan 2 months after the surgery showed a new mass with bone invasion in the posterior right 8th rib.
  • In the CT-guided biopsy of the mass, the spindle cells were positive for CAM5.2. FISH showed a homozygous deletion of CDKN2A (p16), which confirmed sarcomatoid mesothelioma.
  • The patient died two months after the definitive diagnosis, under best supportive care.
  • On retrospective review, the earlier surgical biopsy showed scattered atypical spindle cells in the fibrotic pleural thickening. FISH also detected the CDKN2A (p16) deletion in that sample (data not shown), which the authors took to suggest a continuous neoplastic process.
• The authors' conclusion: The authors concluded that the case shows the need for prompt repeated biopsies in patients with a poor response to treatment for presumed tuberculous pleurisy, and an urgent need to expand access to FISH testing.

Topics

Medical terms in this study, explained in our Lexicon: Sarcomatoid, Mesothelioma, Tuberculous pleurisy, Pleurisy, Pleural Mesothelioma, Pleural Effusion, Thoracoscopy, Biopsy.

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