Comparison of outcomes following a cytological or histological diagnosis of malignant mesothelioma

Our plain-English summary of Comparison of outcomes following a cytological or histological diagnosis of malignant mesothelioma, by S. Muruganandan, H. Alfonso, P. Franklin, et al (British Journal of Cancer, 2017).

The study

• Authors: S. Muruganandan, H. Alfonso, P. Franklin, K. Shilkin, A. Segal, N. Olsen, A. Reid, N. de Klerk, A.B. Musk, F. Brims
• Journal: British Journal of Cancer
• Published: 2017;116(6):703-708
• Cited by: 28 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Survival with the epithelioid subtype of malignant mesothelioma (MM) is longer than the biphasic or sarcomatoid subtypes. There is concern that cytology-diagnosed epithelioid MM may underdiagnose the biphasic subtype. This study examines survival differences between patients with epithelioid MM diagnosed by cytology only and other subtypes diagnosed by histology.

Methods: Demographics, diagnosis method, MM subtype and survival were extracted from the Western Australia (WA) Mesothelioma Registry, which records details of all MM cases occurring in WA.

Results: A total of 2024 MM cases were identified over 42 years. One thousand seven hundred forty-four (86.2%) were male, median (IQR) age was 68.6 (60.4-77.0) years. A total of 1212 (59.9%) cases were identified as epithelioid subtype of which 499 (41.2%) were diagnosed using fluid cytology only. Those with a cytology-only diagnosis were older than the histology group (median 70.2 vs 67.6 years, P<0.001), but median survival was similar (cytology 10.6 (5.5-19.2) vs histology 11.1 (4.8-19.8) months, P=0.727) and Cox regression modelling adjusting for age, sex, site and time since first exposure showed no difference in survival between the different diagnostic approaches.

Conclusions: Survival of cytologically and histologically diagnosed epithelioid MM cases does not differ. A diagnostic tap should be considered adequate to diagnose epithelioid MM without need for further invasive testing.

In plain English

Using the Western Australia Mesothelioma Registry, the authors compared survival in epithelioid malignant mesothelioma (MM) diagnosed only from cells in body fluid (cytology) with cases diagnosed from tissue (histology). The registry held 2024 MM cases over 42 years, and 86.2% were male. Of 1212 epithelioid cases, 499 were diagnosed by fluid cytology only. This group was older (median 70.2 vs 67.6 years). Median survival in the two epithelioid groups was 10.6 and 11.1 months, with no statistically significant difference (P = 0.73). The article assigns these two figures to the groups inconsistently. After adjusting for age, sex, site and time since first exposure, the hazard ratio for a cytology diagnosis was 1.01 (95% CI 0.88 to 1.15). Survival differed significantly between cytology-only cases and biphasic (median 7.8 months) or sarcomatoid (4.0 months) cases. The authors concluded that, in an experienced laboratory, a cytological diagnosis of epithelioid MM may be sufficient without further invasive testing. They noted that both groups may contain some biphasic cases and that treatment and staging data were unavailable.

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 analysis of population-based registry data comparing survival by method of diagnosis
• Who was studied: 2024 confirmed malignant mesothelioma cases (1744 male) recorded on the Western Australia Mesothelioma Registry over 42 years, with follow-up censored on 31 December 2012. Of these, 1888 were pleural and 136 peritoneal.
• Exposure: The comparison was by method of diagnosis: effusion cytology only versus histology. For asbestos, among the 1750 cases with a known exposure source, 1467 (83.8%) had occupational exposure. Ex-Wittenoom miners and township residents made up 25.9% of the cohort; the authors describe Wittenoom exposure as heavy and exclusively crocidolite.
• Main results:
  • 1212 (59.9%) of all cases were epithelioid MM. Of these, 499 (41.2%) were diagnosed by effusion cytology only.
  • Among epithelioid cases, those diagnosed by cytology only were older (median 70.2 vs 67.6 years). The authors found no difference between the two groups in any other characteristic.
  • Overall survival did not differ significantly between epithelioid cases diagnosed by histology and by cytology only (P = 0.73, log rank test).
  • Median survival in the two epithelioid groups was 10.6 (IQR 5.5 to 19.2) and 11.1 (IQR 4.8 to 19.8) months. Table 2 gives 10.6 months for the histology group, while the abstract gives 10.6 months for the cytology group.
  • Survival of cytology-only epithelioid cases differed significantly from biphasic and sarcomatoid cases (P = 0.0001). Median survival was 7.8 months for biphasic cases (n = 412) and 4.0 months for sarcomatoid cases (n = 260).
  • In a multivariable Cox model of the 1212 epithelioid cases, a cytology diagnosis was not associated with survival (HR 1.01, 95% CI 0.88 to 1.15, P = 0.92). Increasing age, male sex (HR 1.42, 95% CI 1.16 to 1.75) and peritoneal MM (HR 2.25, 95% CI 1.74 to 2.91) were associated with shorter survival.
  • Among the 102 epithelioid peritoneal MM cases, survival did not differ significantly by method of diagnosis (histology 5.0 vs cytology-only 4.5 months, P = 0.43).
  • Median survival of epithelioid cases rose with decade of diagnosis, from 7.6 months in 1970 to 1980 to 11.8 months in 2000 to 2012. This trend was not statistically significant (P = 0.083), and the authors considered it likely to represent lead-time bias.
• The authors' conclusion: The authors concluded that survival of cytology-only and histologically diagnosed epithelioid MM does not differ. In their view, in an experienced laboratory a cytological diagnosis of epithelioid MM is clinically acceptable and may be sufficient for clinical management without further invasive testing.
• Limitations the authors state:
  • Some true MM cases in the state may have been missed or misclassified as secondary pleural cancer.
  • The older cytology group may have been more unwell and unable to undergo more invasive diagnostic tests.
  • Some cytology-diagnosed epithelioid cases were likely biphasic; the authors note this is equally true of biopsy specimens.
  • The study design could not assess the accuracy, sensitivity or specificity of either diagnostic method. The registry also does not record whether a case's subtype was changed after expert review or post-mortem.
  • No data on treatment or disease staging were available.
  • The study does not show that cytology-only and histologically diagnosed epithelioid MM are biologically the same.

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: Mesothelioma, Epithelioid, Biphasic Mesothelioma, Sarcomatoid, Cytology, Histology, Fluid Cytology, Median Overall Survival.

Related studies

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• An update on pleuro-pulmonary cytopathology: Part i: Cytological diagnosis of mesothelioma and molecular cytology of lung cancer with an historical perspective — C.W. Bedrossian (2015)
• Applying Probe Electrospray Ionization Mass Spectrometry to Cytological Diagnosis: A Preliminary Study by Using Cultured Lung Cancer Cells — Y. Morimoto, T. Oya, et al. (2021)
• Re-evaluation of histological diagnoses of malignant mesothelioma by immunohistochemistry — H.P. Sandeck, O.D. Røe, et al. (2010)
• Modified Liquid-Based Cytology Technique for Immunocytochemistry in Effusion Specimen — N. Patarapadungkit, P. Jangsiriwitayakorn, et al. (2019)
• Adenomatoid mesothelioma with intranuclear inclusion bodies: a case report with cytological and histological findings — T. Kawai, K. Kawashima, et al. (2014)

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