Malignant mesothelioma with heterologous elements: clinicopathological correlation of 27 cases and literature review

Our plain-English summary of Malignant mesothelioma with heterologous elements: clinicopathological correlation of 27 cases and literature review, by S. Klebe, A. Mahar, D.W. Henderson, et al (Modern Pathology, 2008).

The study

• Authors: S. Klebe, A. Mahar, D.W. Henderson, V.L. Roggli
• Journal: Modern Pathology
• Published: 2008;21(9):1084-94
• Cited by: 48 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Only a small number of malignant mesotheliomas with heterologous elements have been described. There are currently no criteria for diagnosis and little data regarding prognosis. We suggest that the term heterologous mesothelioma should be reserved for tumours that show malignant heterologous elements, notably osteosarcomatous, chondrosarcomatous, or rhabdomyoblastic elements but have immunohistochemical and clinical characteristics of mesothelioma. We identified 27 such cases and characterized the clinical and pathological characteristics of these tumours. In our series, 89% originated in the pleura, and 11% from the peritoneal cavity. The median age at diagnosis was 68 years, ranging from 27 to 85 years. Of these cases, 93% occurred in males and 7% in women. Of the 27 mesothelioma cases 16 (59%) were sarcomatoid, 10 (37%) were biphasic, and one was reported as epithelioid; 40% (11 cases) showed osteosarcomatous elements only, 19% showed areas of rhabdomyosarcoma only, 19% contained areas of chondrosarcoma only, and 22% exhibited osteochondromatous elements. Immunohistochemical labelling for cytokeratins was present in the majority of cases. Exposure to asbestos was identified in all the 17 cases for which an exposure history was available (63%). Median survival was 6 months after diagnosis, similar to the survival seen in sarcomatoid mesotheliomas. The differential diagnosis includes primary and secondary pleural sarcomas, including osteosarcomas and chondrosarcomas. Immunohistochemical labelling for cytokeratins is helpful in the distinction, but lack of labelling for cytokeratins in a spindle cell/sarcomatoid tumour does not exclude the diagnosis of mesothelioma, irrespective of the presence of heterologous elements. We suggest that if the anatomical distribution conforms to that of mesothelioma, a diagnosis of heterologous mesothelioma should be made in preference to a diagnosis of primary pleural osteosarcoma or chondrosarcoma, regardless of cytokeratin positivity, as for conventional non-heterologous sarcomatoid mesothelioma.

In plain English

This article described 27 cases of malignant mesothelioma containing malignant 'heterologous' elements, meaning areas resembling bone cancer (osteosarcoma), cartilage cancer (chondrosarcoma) or muscle cancer (rhabdomyosarcoma). It also reviewed earlier published cases. The cases came from Duke University Medical Center (USA) and Flinders Medical Centre (Australia), including consultation and some medicolegal referral files. At Duke, 19 of 2694 mesotheliomas (0.6%) had such elements. The authors estimated about 0.5% overall, noting their referral centres may overestimate this. Of the 27 tumours, 24 arose in the pleura and 3 in the peritoneum. Twenty-five patients were men, and the median age was 68 years. Sixteen tumours were sarcomatoid and 10 biphasic. One was reported as epithelioid, based on a needle biopsy that may not have represented the tumour. Asbestos exposure was confirmed in all 17 cases for which an exposure history had been obtained. Among 12 patients with outcome data, median survival was 6 months. The authors concluded that these tumours show similar clinical characteristics to other mesotheliomas, including a relationship to asbestos exposure, with survival most like sarcomatoid mesothelioma. They proposed diagnostic criteria.

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 series (clinicopathological review of 27 cases) with a review of previously published cases
• Who was studied: 27 patients with mesothelioma containing malignant heterologous elements. Cases were drawn from departmental archives, consultation cases and some medicolegal referral files at Duke University Medical Center (1982–2008) and Flinders Medical Centre, Adelaide (1998–2008), plus two earlier cases. 24 were pleural and 3 peritoneal; 25 patients were men and 2 women. Median age was 68 years (range 27–85).
• Exposure: Asbestos exposure history where available. Listed sources included shipyard work, a nylon plant, construction, carpentry, electrician and Navy work, maintenance, truck driving, bus mechanic work, household exposure (spouse at a power plant) and environmental exposure. Fibre analysis was done in three cases. Two showed a mixture of fibre types: amosite and crocidolite in both, plus tremolite, anthophyllite and actinolite in one. The third was within the background range despite a positive exposure history.
• Main results:
  • Heterologous elements were found in 19 of 2694 mesothelioma cases at Duke University Medical Center (0.6%) and in 6 of 594 consecutive malignant mesotheliomas at Flinders Medical Centre (1%).
  • Of the 27 cases, 24 (89%) arose in the pleural cavity and 3 (11%) in the peritoneal cavity.
  • Asbestos exposure was confirmed in all 17 cases for which an exposure history had been obtained (63% of all cases). Parietal pleural plaques were identified in nine of those patients.
  • Of the 27 tumours, 16 (59%) were sarcomatoid and 10 (37%) were biphasic.
  • One case was reported as epithelioid. That diagnosis was based on a needle biopsy that may not have adequately represented the tumour, and no follow-up biopsy was available.
  • Of the 27 cases, 11 had osteosarcomatous elements only, 5 had rhabdomyosarcoma only, 5 had chondrosarcoma only, and 6 had a mixture of heterologous elements.
  • Of 23 tumours tested for cytokeratins, 20 showed at least focal labelling.
  • Outcome information was available for 12 of the 27 cases. Median survival was 6 months after diagnosis, and only one patient was confirmed alive after 1 year.
• The authors' conclusion: The authors concluded that heterologous mesothelioma is a rare subtype that shows similar clinical characteristics to other mesotheliomas, including a relationship to asbestos exposure. They found its survival most akin to that of sarcomatoid mesothelioma. They recommended that where the anatomical distribution conforms to that of mesothelioma, the tumour be diagnosed as heterologous mesothelioma rather than primary pleural osteosarcoma or chondrosarcoma, regardless of cytokeratin positivity.
• Limitations the authors state:
  • Many cases were consultation cases, so only limited immunohistochemical studies were available, and some stains had been performed in other laboratories.
  • Exposure information was missing for many cases, so the data likely underestimate asbestos exposure.
  • Both centres are major mesothelioma referral centres, so the frequency figure may overestimate the true prevalence.
  • The single epithelioid case was diagnosed on a needle biopsy that may not have represented the tumour adequately.
  • Only limited clinical information was available for the two earlier cases.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Mesothelioma, Peritoneal mesothelioma.

Medical terms in this study, explained in our Lexicon: Malignant Mesothelioma, Heterologous Elements, Prognosis, Mesothelioma, Pleura, Peritoneal Cavity, Sarcomatoid, Biphasic Mesothelioma.

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