The value of cytology in distinguishing malignant mesothelioma: An institutional experience of 210 cases reclassified according to the International System for Reporting Serous Fluid Cytopathology (ISRSFC)

Our plain-English summary of The value of cytology in distinguishing malignant mesothelioma: An institutional experience of 210 cases reclassified according to the International System for Reporting Serous Fluid Cytopathology (ISRSFC), by P. Straccia, D. Magnini, R. Trisolini, et al (Cytopathology, 2022).

The study

• Authors: P. Straccia, D. Magnini, R. Trisolini, F. Lococo, M. Chiappetta, A. Cancellieri
• Journal: Cytopathology
• Published: 2022;33(1):77-83
• Cited by: 9 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objective: Malignant mesothelioma (MM) is usually diagnosed by histological examination of tissue samples; however, effusion cytology offers an opportunity to identify a strong possibility for mesothelioma diagnosis at an early stage. We conducted a retrospective analysis of cytological specimens from a large series of histologically proven MM diagnosed over 19 years. The cases were reviewed and reclassified according to the International System for Reporting Serous Fluid Cytopathology (ISRSFC).

Methods: A total of 450 cases were identified. Cytological analysis was present in 210 patients (164 pleural and 46 peritoneal effusions). All cases were reviewed and reclassified according to the proposed ISRSFC scheme. A comparison among the cytomorphological features was made throughout the different diagnostic categories.

Results: The 210 cases were histologically diagnosed as follows: 192 (91.4%) cases had an epithelioid type and 18 (8.6%) had a sarcomatoid subtype of MM. The cytological cases were reclassified as follows: 2 (0.9%) as non-diagnostic (ND), 81 (38.6%) as negative for malignancy (NFM), 4 (1.9%) as atypia of undetermined significance (AUS), 11 (5.2%) as suspicious for malignancy (SFM), 112 (53.4%) as malignant (MAL). Sarcomatoid cells in the MAL category were characterised cytomorphologically by more pronounced discohesion. In comparison with the epithelioid subtype, the tumour cells appeared solitary with moderate or marked nuclear pleomorphism, and irregular chromatin.

Conclusions: It is important to recognise the cytological characteristics of this aggressive entity to suggest an early and precise possible diagnosis. Morphological features, coupled with clinico-radiological data may help the clinicians in adequately managing the patients.

© 2021 John Wiley & Sons Ltd.

In plain English

This retrospective study searched the pathology database of Gemelli Hospital in Rome, Italy, from January 2000 to December 2019 and found 450 confirmed malignant mesothelioma cases. Of these, 210 patients had fluid samples examined under the microscope (cytology): 164 from the pleura and 46 from the peritoneum. On tissue diagnosis, 192 of the 210 were epithelioid and 18 were sarcomatoid. The authors re-sorted the 210 samples into the five categories of a proposed international reporting system: 112 (53.4%) malignant, 11 (5.2%) suspicious for malignancy, 4 (1.9%) atypia of undetermined significance, 81 (38.6%) negative for malignancy and 2 (0.9%) non-diagnostic. Samples were classed malignant in 98 of 164 pleural cases and 14 of 46 peritoneal cases. No statistically significant survival difference was found between patients diagnosed with cytology and those with tissue diagnosis only. Median survival was shorter for peritoneal than for pleural cases (4.2 vs 8.3 months). The authors concluded that, with supporting clinical and laboratory findings, cytology can give a definite diagnosis in a subset of patients. The article did not report patients' asbestos exposure.

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 review of cytology samples from patients with tissue-confirmed malignant mesothelioma, reclassified using the proposed International System for Reporting Serous Fluid Cytopathology (ISRSFC)
• Who was studied: 450 patients with confirmed malignant mesothelioma (265 men, 185 women; median age 78) from the pathology database of Gemelli Hospital, Catholic University, Rome, Italy, 2000 to 2019. 210 of them had cytology: 164 pleural and 46 peritoneal effusion samples.
• Exposure: Not studied. The article does not report patients' asbestos or other exposures. The study compared fluid cytology categories with tissue diagnosis.
• Main results:
  • Of the 210 cytology samples, 2 (0.9%) were reclassified as non-diagnostic, 81 (38.6%) as negative for malignancy, 4 (1.9%) as atypia of undetermined significance, 11 (5.2%) as suspicious for malignancy, and 112 (53.4%) as malignant.
  • On tissue diagnosis, the 210 cases with cytology were 192 (91.4%) epithelioid and 18 (8.6%) sarcomatoid mesothelioma.
  • The authors report a malignancy rate of 59.7% for pleural effusions and 30.4% for peritoneal effusions. Table 1 lists 98 of 164 pleural samples (59.8%) and 14 of 46 peritoneal samples (30.4%) as malignant.
  • The authors report a sensitivity of cytology for diagnosing mesothelioma of 64.4% for pleural fluid and 34% for peritoneal effusions.
  • There was no statistically significant difference in survival between patients diagnosed with cytology and those with histological biopsies (P = .68). Table 3 gives survival of 11.9 months for epithelioid cases with cytology and 4.5 months for sarcomatoid cases with cytology, versus 11.2 and 4.3 months with histology only.
  • Among peritoneal mesothelioma cases (46), median survival was shorter than in pleural mesothelioma: 4.2 versus 8.3 months, P less than .005.
  • In the malignant category, sarcomatoid tumour cells were more discohesive than epithelioid cells. They appeared mainly isolated, with moderate or marked nuclear pleomorphism and irregular chromatin.
• The authors' conclusion: The authors concluded that their data showed satisfactory and reliable results for effusion cytology in diagnosing malignant mesothelioma. In their opinion, a definite diagnosis can be made by cytology in a subset of patients if it is adequately supported by clinical data and immunohistochemical or molecular findings.
• Limitations the authors state:
  • Final ISRSFC criteria were still under discussion, so the authors used their own interim criteria for reclassification.
  • Only definitively malignant results were counted as positive, which the authors note gives a markedly lower sensitivity than studies that also count suspicious results.
  • The authors note a broad morphological overlap between reactive mesothelial cells and malignant mesothelioma cells.

Topics

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

Medical terms in this study, explained in our Lexicon: Cytology, Mesothelioma, Serous Fluid, Epithelioid, Sarcomatoid, Nuclear Pleomorphism.

Related studies

• The role of liquid-based cytology and ancillary techniques in pleural and pericardic effusions: an institutional experience — E.D. Rossi, T. Bizzarro, et al. (2015)
• Categorical systems for reporting of cytology specimens: Following the footsteps of Bethesda-like reporting systems — L.J. Layfield, Z. Baloch (2020)
• 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)
• Root cause analysis of indeterminate diagnoses in serous fluids cytopathology — H.N. Gokozan, A. Harbhajanka, et al. (2021)
• 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. Hjerpe, V. Ascoli, et al. (2015)

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