A challenging diagnosis of malignant mesothelioma with osteosarcomatous differentiation metastasizing to bone

Our plain-English summary of A challenging diagnosis of malignant mesothelioma with osteosarcomatous differentiation metastasizing to bone, by M. Brown, H. Jersmann, T. Crowhurst, et al (Respirology Case Reports, 2020).

The study

• Authors: M. Brown, H. Jersmann, T. Crowhurst, C. Van Vliet, G. Crouch, A. Badiei
• Journal: Respirology Case Reports
• Published: 2020;8(8):e00664
• Type of article: Case report
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Malignant pleural mesothelioma (MPM) is an insidious primary neoplasm of the pleura that can be challenging to diagnose and is commonly considered to be only locally invasive. We present the case of a 74-year-old male who presented with clinical features of MPM but from whom pleural fluid and biopsies initially suggested benign pathology. He later developed diffuse bony metastases and re-examination of pleural biopsies using modern immunohistochemistry and molecular testing revealed a diagnosis of sarcomatoid and desmoplastic MPM with heterologous osteosarcomatous differentiation. This case not only demonstrates the rare potential of skeletal metastasis of MPM, but also highlights the importance of recognizing the utility of modern diagnostic tests and their potential to prevent the need for unnecessary invasive procedures. To our knowledge this is the first description of this rare histological sub-type presenting with skeletal metastases.

© 2020 The Authors. Respirology Case Reports published by John Wiley & Sons Australia, Ltd on behalf of The Asian Pacific Society of Respirology.

In plain English

This is a case report of one patient, along with the authors' search of earlier published case reports. The patient was a 74-year-old man and former smoker (five pack-years) who had twelve months of worsening breathlessness. He had 18 months of asbestos exposure in the 1960s as a maintenance fitter cutting asbestos sheets. The article does not name a fiber type. Pleural biopsies taken twice, the second time during open chest surgery, were first read as benign inflammation (fibrinous pleuritis). A second-opinion review used a genetic test (FISH). It found homozygous loss (loss of both copies) of the CDKN2A gene in three separate biopsy samples, and the diagnosis became sarcomatoid and desmoplastic mesothelioma with osteosarcomatous (bone-forming) differentiation. The patient declined chemotherapy. Nine months after his first tests, scans showed widespread lesions in his ribs, breastbone and spine. A breastbone biopsy was consistent with metastatic mesothelioma. The authors found 18 earlier English-language case reports of mesothelioma spreading to bone. They stated that none described this subtype spreading to bone. They concluded that BAP-1 and CDKN2A testing can be invaluable and may avoid unnecessary invasive investigations.

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 a single patient, with a search of previously published case reports
• Who was studied: One 74-year-old man, a reformed smoker (five pack-years) who had immigrated to Australia from the United Kingdom in 1968, with progressive breathlessness over twelve months
• Exposure: 18 months of asbestos exposure as a maintenance fitter in the 1960s, cutting asbestos sheets; no fiber type is given
• Main results:
  • Parietal pleural biopsies taken at pleuroscopy showed mild atypia favoured to represent fibrinous pleuritis (a benign condition)
  • Biopsies from a later right thoracotomy were also initially read as favouring benign pleuritis
  • On second-opinion review, FISH showed homozygous loss of CDKN2A at 9p21 in three separate biopsy samples, while BAP-1 expression was preserved
  • The diagnosis was changed to sarcomatoid and desmoplastic mesothelioma with heterologous osteosarcomatous differentiation
  • The patient declined chemotherapy
  • Nine months after initial investigations, CT showed widespread lytic lesions of the right ribs and sternum and many sclerotic lesions in the spine
  • A CT-guided biopsy of the sternum showed features consistent with metastatic malignant pleural mesothelioma with sarcomatoid and desmoplastic patterns
  • The authors identified 18 earlier case reports in the English literature of mesothelioma spreading to the skeleton
  • The authors stated that, to their knowledge, no reports had described bony metastases in this histological sub-type
• The authors' conclusion: The authors concluded that modern immunohistochemistry for BAP-1 protein loss and FISH for homozygous deletion of CDKN2A can be invaluable in diagnosing mesothelioma and may avoid unnecessary invasive investigations

Topics

Medical terms in this study, explained in our Lexicon: Mesothelioma, Pleural Mesothelioma, Neoplasm, Pleura, Pathology, Immunohistochemistry, Molecular Profiling, Sarcomatoid.

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