Pleural malignant mesothelioma versus pleuropulmonary synovial sarcoma: a clinicopathological study of 22 cases with molecular analysis and survival data

Our plain-English summary of Pleural malignant mesothelioma versus pleuropulmonary synovial sarcoma: a clinicopathological study of 22 cases with molecular analysis and survival data, by S. Klebe, S. Prabhakaran, A. Hocking, et al (Pathology, 2018).

The study

• Authors: S. Klebe, S. Prabhakaran, A. Hocking, E. Pulford, S. Moore, M. Nicola, P.W. Allen, D.W. Henderson
• Journal: Pathology
• Published: 2018;50(6):629-634
• Cited by: 10 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The aim of this study was to carry out a comparative analysis by transducin-like enhancer of split 1 (TLE1) immunohistochemistry and molecular analysis of SYT-SSX, for 16 pleural predominantly sarcomatoid mesotheliomas and six cases of pleuropulmonary synovial sarcoma (five pleural in distribution only, with one case of a predominantly subpleural upper lobe synovial sarcoma), all of which were solely or predominantly monophasic. Our comparison included survival and some clinical data. We consider that the following points emerged from this study.

Copyright © 2018 Royal College of Pathologists of Australasia. Published by Elsevier B.V. All rights reserved.

In plain English

This retrospective South Australian study reviewed 22 primary pleural or subpleural tumours from 2005 to 2018 where synovial sarcoma was considered. Using FISH or RT-PCR for the SYT-SSX gene change, the authors classed 16 as predominantly sarcomatoid pleural mesothelioma (all negative) and six as synovial sarcoma (all positive). Mean ages were 72 and 44 years respectively. Median survival was 4.5 months for mesothelioma (95% confidence interval 2.96 to 9.42 in the table, about 3.0 to 5.0 in the discussion) and over 48 months for synovial sarcoma, with four patients alive; survival differed (p = 0.014). TLE1 staining was positive in all six synovial sarcomas but also 7 of 16 mesotheliomas. Asbestos exposure was recorded in 10 of 16 mesothelioma patients (absent in 3, unknown in 3) and 1 of 6 synovial sarcoma patients (absent in 2, unknown in 3). One synovial sarcoma, in an elderly man with brief past work exposure, initially resembled mesothelioma. The authors concluded molecular testing is mandatory to distinguish them, which matters for compensation because pleural synovial sarcoma has no consistent or proven causal link to asbestos.

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: Retrospective clinicopathological case series comparing two tumour types, using immunohistochemistry, molecular testing and survival data
• Who was studied: 22 primary malignancies (21 pleural only, one in the subpleural zone of an upper lobe), seen in-house or referred during 2005 to 2018 in South Australia. Molecular testing classed 16 as predominantly sarcomatoid malignant mesothelioma and six as synovial sarcoma. Only cases with SYT-SSX molecular testing, clinical follow-up, and tissue for further staining were included.
• Exposure: The study compared diagnostic tests rather than an exposure: TLE1 immunohistochemistry and molecular detection of the t(X;18) translocation (SYT-SSX) by FISH and/or RT-PCR. Asbestos exposure history and pleural plaques were recorded as clinical features. For mesothelioma, exposure was yes/no/no data 10/3/3; for synovial sarcoma it was 1/2/3.
• Main results:
  • Mean age was 72 years (range 56 to 88) for the 16 mesothelioma patients and 44 years (range 9 to 72) for the 6 synovial sarcoma patients.
  • Table 1 gives median survival of 4.5 months (95% CI 2.96 to 9.42) for mesothelioma. The Discussion gives this interval as about 3.0 to 5.0, and the article does not explain the difference. Median survival for synovial sarcoma was more than 48 months, with 4 patients alive. Mean overall survival was 9.2 plus or minus 2.1 months for mesothelioma and 136.2 plus or minus 35.1 months for synovial sarcoma. The Kaplan–Meier survival comparison between the groups gave p = 0.014.
  • TLE1 staining was positive in all 6 synovial sarcomas and also in 7 of 16 sarcomatoid mesotheliomas (about 44%). The authors judged it of little value for telling the tumours apart.
  • SYT-SSX testing was negative in all 16 mesotheliomas and positive in all 6 synovial sarcomas. This was the basis on which the cases were classified.
  • Asbestos exposure (yes/no/no data) was 10/3/3 among the 16 mesothelioma patients and 1/2/3 among the 6 synovial sarcoma patients.
  • One mesothelioma, in a patient with past asbestos exposure but no pleural plaques on imaging, was first favoured as pleural synovial sarcoma. It later tested negative for SYT-SSX by both FISH and RT-PCR, and micro-RNA analysis was consistent with mesothelioma.
  • In one synovial sarcoma case, an elderly man with brief, long-past occupational asbestos exposure, the microscopic appearance favoured sarcomatoid mesothelioma, but FISH showed SYT-SSX. This patient had a short survival.
• The authors' conclusion: The authors concluded that clinical, radiological and histological findings, including immunohistochemistry, do not allow definitive distinction between malignant mesothelioma and synovial sarcoma, and that molecular analysis is mandatory for this distinction. They stated that correct diagnosis matters for compensation, because pleural synovial sarcomas have no consistent or proven causal relationship to asbestos exposure, in contrast to the majority of pleural malignant mesotheliomas.
• Limitations the authors state:
  • Because of insufficient remaining tissue, additional immunohistochemistry could not be done on some cases, so some results relied on the referring laboratory's findings.
  • Data were missing for some cases; for example, no calretinin data were available for 4 of the 6 synovial sarcomas.

Topics

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

Medical terms in this study, explained in our Lexicon: Malignant Mesothelioma, Synovial Sarcoma, Immunohistochemistry, Sarcomatoid, Mesothelioma.

Related studies

• TLE1 is expressed in the majority of primary pleuropulmonary synovial sarcomas — L.S. Lino-Silva, J.P. Flores-Gutiérrez, et al. (2011)
• NY-ESO-1 expression in synovial sarcoma and other mesenchymal tumors: significance for NY-ESO-1-based targeted therapy and differential diagnosis — J.P. Lai, P.F. Robbins, et al. (2012)
• Challenges and controversies in the diagnosis of malignant mesothelioma: Part 2. Malignant mesothelioma subtypes, pleural synovial sarcoma, molecular and prognostic aspects of mesothelioma, BAP1, aquaporin-1 and microRNA — D.W. Henderson, G. Reid, et al. (2013)
• Pericardial synovial sarcoma, a potential for misdiagnosis: clinicopathologic and molecular cytogenetic analysis of three cases with literature review — Y. Cheng, W. Sheng, et al. (2012)
• The diagnostic utility of reduced immunohistochemical expression of SMARCB1 in synovial sarcomas: a validation study — J. Ito, N. Asano, et al. (2016)
• Synovial sarcoma of the pleura and its differentiation from other primary pleural tumours: a clinicopathological and immunohistochemical review of three cases — A.G. Nicholson, P. Goldstraw, et al. (1998)

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