Mesothelioma

Our plain-English summary of Mesothelioma, by N. Rao, S. Wei (CytoJournal, 2022).

The study

• Authors: N. Rao, S. Wei
• Journal: CytoJournal
• Published: 2022;19:10
• Type of article: Review
• Cited by: 7 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Mesothelioma arises from the surface serosal cells lining the pleural, peritoneal, and pericardial cavities. It has three variants including: epithelioid, sarcomatous/desmoplastic, and biphasic types. Mesothelioma cells, predominantly of the epithelioid type, can shed into effusions as sheets, clusters/ morulae, papillae, or single cells. The challenges to cytologic diagnosis of mesothelioma are two-fold: 1. distinguishing mesothelial cells from metastatic malignant (most commonly carcinoma) cells; 2. distinguishing reactive mesothelial from mesothelioma cells. Immunocytochemistry is a helpful aid to cytologic evaluation for the former. The distinction of reactive mesothelial cells from mesothelioma can be more difficult, as there is considerable overlap in their appearances in effusion specimens. Recently developed ancillary molecular and genetic tests are proving to be useful in confirming the diagnosis of malignant mesothelioma in cytology specimens.

© 2022 Cytopathology Foundation Inc, Published by Scientific Scholar.

In plain English

This article was a review, written as a chapter of a book on serous fluid cytology. It described how mesothelioma is diagnosed from cells in effusions, which is fluid that collects around the lungs or in the abdomen. It reported no new patients or data. The authors described the cell features pathologists look for. Epithelioid mesothelioma sheds many cells into fluid, while spindle cells from sarcomatoid and biphasic types usually do not. They compared mesothelioma cells with reactive (non-cancerous) mesothelial cells and with adenocarcinoma, and covered rare variants, special stains, immunocytochemistry and genetic tests. Citing earlier work, they reported that conventional cytology detected malignant cells in effusions with a sensitivity of around 58% (average from 6001 cases in six studies) and a specificity of 97%. They also cited loss of BAP1 staining in 60% to 70% of epithelioid mesotheliomas. They outlined a stepwise testing approach using BAP1, MTAP and CDKN2A, and noted that intact results cannot exclude mesothelioma. Asbestos was mentioned only in passing. The authors concluded that newer molecular and genetic tests are proving useful in confirming 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: Narrative review (book chapter published as a review article) on the cytologic diagnosis of mesothelioma in effusion fluids; no original study data
• Who was studied: No patients or cases were studied. The review covers mesothelioma as seen in pleural and peritoneal effusion specimens, illustrated with example images.
• Exposure: Not studied. The review mentions only in passing, citing an earlier report, that a strong link between mesothelioma and asbestos exposure was first reported in 1960. No fiber types are named.
• Main results:
  • The review describes mesothelioma effusions as hypercellular, with three-dimensional groups that have knobby outlines. By contrast, benign effusions are less cellular, with smaller, largely two-dimensional cell groups.
  • The review describes adenocarcinoma cell groups as keeping a smooth contour ('community border'), unlike the knobby outlines of mesothelioma cell groups.
  • Citing an earlier source, the review reports that conventional cytology detected malignant cells in effusion fluids (not specifically mesothelioma) with a sensitivity of around 58% (average from 6001 cases in six studies) and a specificity of 97%.
  • Citing earlier work, the review states that loss of nuclear BAP1 staining is found in 60% to 70% of epithelioid mesotheliomas and is highly specific, and that loss of MTAP staining is very specific for mesothelioma.
  • The review presents a suggested stepwise work-up: a panel of three carcinoma and two mesothelial markers plus BAP1, then MTAP or CDKN2A FISH if BAP1 is intact. It notes that intact BAP1 and CDKN2A do not exclude mesothelioma.
• The authors' conclusion: The authors concluded that telling reactive mesothelial cells from mesothelioma in effusions can be difficult because of overlapping appearances, and that recently developed molecular and genetic tests are proving useful in confirming malignant mesothelioma in cytology specimens.

Topics

Medical terms in this study, explained in our Lexicon: Mesothelioma, Pericardial, Epithelioid, Desmoplastic Mesothelioma, Biphasic Mesothelioma, Papillae, Mesothelial Cells, Carcinoma.

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