Cytological diagnosis of mesothelioma in situ versus invasive mesothelioma

Our plain-English summary of Cytological diagnosis of mesothelioma in situ versus invasive mesothelioma, by A. Churg, F. Galateau-Salle, L. Tan, et al (Pathology, 2022).

The study

• Authors: A. Churg, F. Galateau-Salle, L. Tan, G. Qing
• Journal: Pathology
• Published: 2022;54(1):133-136
• Type of article: Case report, Letter
• Cited by: 6 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Summary of the article

In this letter, the authors asked whether pleural effusion cytology can distinguish mesothelioma in situ from invasive mesothelioma when there is no radiological or direct visual evidence of tumour. Responding to an earlier report by Pulford et al., they described a patient they had previously reported as having mesothelioma in situ. The patient presented in 2014 at age 70 with a right pleural effusion of unknown aetiology. It was drained repeatedly over 4 years and recurred rapidly each time. Until 2018, imaging showed only an effusion, with no pleural thickening. All pleural fluid cytology specimens showed multiple balls of slightly atypical mesothelial cells. A 2015 cell block, stained retrospectively, showed loss of BAP1. Pleural biopsies in 2016 and 2017, from pleura the operator reported as visually normal, showed mesothelioma in situ with BAP1 loss. In 2018, imaging first showed pleural thickening, the effusion had become haemorrhagic, and a biopsy revealed invasive mesothelioma. The authors considered it extremely unlikely that invasive disease had been missed over 4 years. They noted an arguable subtle increase in atypia over time, but judged all samples malignant and meeting guideline criteria for mesothelioma. They concluded that when there is only an effusion and no tumour on imaging or direct inspection, a diagnosis such as 'at least mesothelioma in situ, cannot exclude invasive diffuse mesothelioma' would be appropriate, because mesothelioma in situ is in theory potentially treatable and curable.

PubMed has no abstract for this study, and the article doesn't print one. We wrote this summary from the full article with the help of AI. It is not the authors' wording.

In plain English

This letter to the editor reported one patient's case; it gives no rates. The patient first presented in 2014 at age 70 with fluid around the right lung (a pleural effusion) of unknown cause. The fluid kept returning after drainage for 4 years. Until 2018, imaging showed only the fluid, with no pleural thickening. Every fluid sample contained balls of slightly atypical mesothelial cells. A 2015 sample, stained later, showed loss of a protein called BAP1. Biopsies in 2016 and 2017, taken from pleura the operator described as visually normal, showed mesothelioma in situ, an early form limited to the surface lining. In 2018, imaging showed thickening for the first time, and a biopsy showed invasive mesothelioma. In the authors' view, all fluid samples met guideline criteria for mesothelioma, although the earlier ones most probably came from in situ disease. The authors concluded that when there is only fluid and no visible tumour, a report such as 'at least mesothelioma in situ, cannot exclude invasive diffuse mesothelioma' would be appropriate. The letter gave no asbestos exposure history.

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: Letter to the editor (correspondence) describing a single case, previously reported by the same authors as mesothelioma in situ
• Who was studied: One patient, now deceased, who first presented in 2014 at age 70 with a right pleural effusion of unknown cause and was followed with repeated pleural fluid cytology over 4 years
• Exposure: The article does not report any asbestos or other exposure history for the patient
• Main results:
  • The effusion recurred over 4 years. Until 2018, imaging showed only the effusion, with no pleural thickening.
  • All pleural fluid cytology specimens from 2014 to 2018 looked similar, with multiple balls of slightly atypical cells that marked as mesothelial cells.
  • Cell block material from a 2015 fluid specimen, stained retrospectively, showed loss of BAP1.
  • At the 2016 and 2017 pleural biopsies, the operator reported the pleura as visually normal.
  • Both the 2016 and 2017 biopsies showed a pattern of mesothelioma in situ: a single layer of slightly atypical cuboidal mesothelial cells that had lost BAP1.
  • In 2018, imaging showed pleural thickening for the first time and the effusion was haemorrhagic (bloody). A pleural biopsy revealed invasive mesothelioma.
  • The authors saw an arguable subtle increase in cell atypia over the 4 years. In their view, all fluid samples were malignant and met guideline criteria for mesothelioma, even though the earlier samples in all probability came from mesothelioma in situ.
• The authors' conclusion: The authors concluded that a fluid sample from a case with visual or radiological evidence of tumour can be reliably diagnosed as invasive mesothelioma. When there is only an effusion and no visible tumour, they considered a diagnosis along the lines of 'at least mesothelioma in situ, cannot exclude invasive diffuse mesothelioma' appropriate.
• Limitations the authors state:
  • The authors note that invasive tumour may be present for some time before it is visible on imaging or on inspection of the pleura. This makes it hard to be sure whether a fluid sample reflects in situ or subtle invasive disease. In this case they judged it extremely unlikely that invasion was missed over 4 years.
  • The initial 2014 fluid specimen was not well preserved.

Topics

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

Medical terms in this study, explained in our Lexicon: Mesothelioma in Situ, Mesothelioma, Pleural Effusion, Cytology, Pleural Thickening, Fluid Cytology, Mesothelial Cells, Cell Block.

Related studies

• Development of mesothelioma in situ and its progression to invasive disease observed in a patient with uncontrolled pleural effusions for 15 years — K. Hidaka, T. Takeda, et al. (2020)
• Usefulness of p16/CDKN2A fluorescence in situ hybridization and BAP1 immunohistochemistry for the diagnosis of biphasic mesothelioma — D. Wu, K. Hiroshima, et al. (2017)
• BAP1 Immunohistochemistry and p16 FISH in the Diagnosis of Sarcomatous and Desmoplastic Mesotheliomas — H.C. Hwang, S. Pyott, et al. (2016)
• BAP1 immunohistochemistry has limited prognostic utility as a complement of CDKN2A (p16) fluorescence in situ hybridization in malignant pleural mesothelioma — S.M. McGregor, J. McElherne, et al. (2017)
• Fluorescence in situ hybridization (FISH) provides estimates of minute and interstitial BAP1, CDKN2A, and NF2 gene deletions in peritoneal mesothelioma — S. Brich, F. Bozzi, et al. (2020)
• Malignant mesothelioma in situ: diagnostic and clinical considerations — E. Pulford, D.W. Henderson, et al. (2020)

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