Guidelines for the cytopathologic diagnosis of epithelioid and mixed-type malignant mesothelioma. Complementary statement from the International Mesothelioma Interest Group, also endorsed by the International Academy of Cytology and the Papanicolaou Society of Cytopathology

Our plain-English summary of Guidelines for the cytopathologic diagnosis of epithelioid and mixed-type malignant mesothelioma. Complementary statement from the International Mesothelioma Interest Group, also endorsed by the International Academy of Cytology and the Papanicolaou Society of Cytopathology, by A. Hjerpe, V. Ascoli, C.W.M. Bedrossian, et al (Acta Cytologica, 2015).

The study

• Authors: A. Hjerpe, V. Ascoli, C.W.M. Bedrossian, M.E. Boon, J. Creaney, B. Davidson, A. Dejmek, K. Dobra, A. Fassina, A. Field, P. Firat, T. Kamei, T. Kobayashi, C.W. Michael, S. Önder, A. Segal, P. Vielh
• Journal: Acta Cytologica
• Published: 2015;59(1):2-16
• Type of article: Guideline
• Cited by: 60 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objective: To provide practical guidelines for the cytopathologic diagnosis of malignant mesothelioma.

Data Sources: Cytopathologists with an interest in the field involved in the International Mesothelioma Interest Group (IMIG) and the International Academy of Cytology (IAC) contributed to this update. Reference material includes peer-reviewed publications and textbooks.

Rationale: This article is the result of discussions during and after the IMIG 2012 conference in Boston, followed by thorough discussions during the 2013 IAC meeting in Paris. Additional contributions have been obtained from cytopathologists and scientists who could not attend these meetings, with final discussions and input during the IMIG 2014 conference in Cape Town.

© 2015 S. Karger AG, Basel.

In plain English

This article is a consensus guideline, not a study of patients. Cytopathologists from the International Mesothelioma Interest Group and the International Academy of Cytology set out their shared opinion on diagnosing epithelioid and mixed-type malignant mesothelioma from fluid (effusion) samples. The authors recommended confirming every such diagnosis with antibody staining, using a panel of at least four antibodies, two in favor of mesothelioma and two against it. They described optional extra tests. One is fluid hyaluronan above 250 mg/l, which they said is found in only 50–60% of mesothelioma effusions. Another is electron microscopy, which they said is conclusive in some 50% of cases. Citing an earlier study, they stated that effusion cytology with appropriate ancillary techniques can diagnose mesothelioma with a positive predictive value of 100%. They noted that sarcomatoid mesothelioma can rarely be diagnosed this way, and that samples with few cells, bleeding or inflammation are difficult. They also noted that a negative result does not exclude mesothelioma. They stated that a history of asbestos exposure is not required for the diagnosis.

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: Consensus guideline (review-type statement of expert opinion) based on published literature and textbooks; no new patient data
• Who was studied: No patients were studied. The guideline was written by cytopathologists in the International Mesothelioma Interest Group (IMIG) and the International Academy of Cytology (IAC). It came out of discussions at the IMIG 2012 conference in Boston, the 2013 IAC meeting in Paris and the IMIG 2014 conference in Cape Town. It addresses effusions (pleural, peritoneal, pericardial) from patients with possible malignant mesothelioma.
• Exposure: No exposure was studied. The authors stated that a history of asbestos exposure can raise suspicion of mesothelioma but is not required for the diagnosis.
• Main results:
  • Recommendation: every cytological diagnosis of mesothelioma should be confirmed with immunocytochemistry or immunohistochemistry (antibody staining).
  • Recommendation: use a panel of at least four antibodies, two favoring and two against mesothelioma, and never rely on a single stain. The suggested panel is EMA (membranous staining) and calretinin, which are positive in mesothelioma, plus CEA and BerEp4, which are negative in mesothelioma.
  • Fluid hyaluronan: the authors stated that concentrations above 250 mg/l indicate mesothelioma, and that samples with 60–249 mg/l can be tested for mesothelin.
  • The authors stated that such high hyaluronan levels are found in only 50–60% of mesothelioma effusions.
  • Electron microscopy of effusion cells: the authors stated that a conclusive mesothelioma diagnosis can be expected in only about 50% of cases.
  • Molecular testing: a homozygous deletion of the 9p21 band found by FISH supports a mesothelioma diagnosis, but the authors stated it is not pathognomonic (it does not by itself identify mesothelioma).
  • Citing an earlier study (reference 5), the authors stated that effusion cytology with appropriate ancillary techniques can diagnose mesothelioma with a positive predictive value of 100%.
• The authors' conclusion: The authors concluded that cytology's sensitivity for mesothelioma may vary with the cytopathologist's experience, but that its accuracy is unquestioned when these guidelines are followed. In their view this allows an earlier and less invasive diagnosis.
• Limitations the authors state:
  • Sarcomatoid (non-epithelioid) mesothelioma is not detected by effusion cytology.
  • A negative cytology result does not exclude mesothelioma.
  • Cytology may be somewhat less sensitive than histopathology (tissue examination).
  • Samples with few cells, bleeding or inflammation are an obstacle to diagnosis.

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: Epithelioid, Malignant Mesothelioma, Mesothelioma, Cytology, Cytopathology, IMIG.

Related studies

• Guidelines for the cytopathologic diagnosis of epithelioid and mixed-type malignant mesothelioma: Complementary Statement from the International Mesothelioma Interest Group, Also Endorsed by the International Academy of Cytology and the Papanicolaou Society of Cytopathology — A. Hjerpe, V. Ascoli, et al. (2015)
• Guidelines for the cytopathologic diagnosis of epithelioid and mixed-type malignant mesothelioma: Complementary statement from the international mesothelioma interest group, also endorsed by the international academy of cytology and the papanicolaou society of cytopathology. A proposal to be applauded and promoted but which requires updating — M. Sheaff (2020)
• Guidelines for the Cytopathologic Diagnosis of Epithelioid and Mixed-Type Malignant Mesothelioma: a secondary publication — A. Hjerpe, V. Ascoli, et al. (2015)
• Comments on the recently published "Guidelines for the cytopathologic diagnosis of epithelioid and mixed-type malignant mesothelioma" — A. Hjerpe, K. Dobra (2015)
• Cytopathologic Diagnosis of Epithelioid and Mixed-Type Malignant Mesothelioma: Ten Years of Clinical Experience in Relation to International Guidelines — A. Hjerpe, S. Abd-Own, et al. (2018)
• Guidelines for Pathologic Diagnosis of Malignant Mesothelioma 2017 Update of the Consensus Statement From the International Mesothelioma Interest Group — A.N. Husain, T.V. Colby, et al. (2018)

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