Parakeratotic-like cells in effusions - A clue to diagnosis of malignant mesothelioma

Our plain-English summary of Parakeratotic-like cells in effusions - A clue to diagnosis of malignant mesothelioma, by L. Gao, W. Reeves, R.M. Demay (CytoJournal, 2012).

The study

• Authors: L. Gao, W. Reeves, R.M. Demay
• Journal: CytoJournal
• Published: 2012;9:18
• Cited by: 10 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Malignant mesothelioma (MM) is an aggressive neoplasm with a poor prognosis. Its incidence has been increasing worldwide. Cytological examination of an effusion is often the first opportunity to diagnose MM. However, the cytological diagnosis of MM can be difficult. We have noticed that parakeratotic-like cells, with orange cytoplasm and pyknotic nuclei, are present in many cases of mesothelioma on Papanicolaou-stained cytology slides. Although this cytological finding has been described previously, to our knowledge, there has been no systematic study of this finding. Our study is to determine whether the presence of small parakeratotic / orangeophilic cells (PK-like cells) is specific for the cytodiagnosis of mesothelioma.

Materials And Methods: A total of 90 body fluid cases were selected from our archived specimens in the Cytology Section at the University of Chicago Hospital accessioned between January 2000 to November 2011. They included 30 cases of mesothelioma, 30 cases of adenocarcinoma, and 30 cases of reactive mesothelial cells.

Results: PK-like cells were present in 83% of the mesothelioma cases, 13% of the adenocarcinoma cases, and 7% of the reactive cases. Our data showed that the presence of PK-like cells has a specificity of 90%, sensitivity of 83%, positive predictive value of 81%, and negative predictive value of 84% for the diagnosis of malignant mesothelioma in body cavity fluids.

Conclusion: The presence of PK-like cells in the effusion specimen, especially in pleural effusions, is a highly specific and moderately sensitive cytological feature for diagnosis of mesothelioma.

In plain English

This University of Chicago study asked whether a particular cell seen under the microscope helps diagnose malignant mesothelioma in fluid from around the lungs, abdomen or heart. It did not study asbestos or any other exposure. The authors reviewed stored, Papanicolaou-stained fluid samples from 2000 to 2011: 30 from patients with mesothelioma (all of the epithelioid type, 24 from pleural fluid), 30 from adenocarcinoma and 30 with reactive mesothelial cells. They looked for small "parakeratotic-like" cells with orange-stained cytoplasm and shrunken, degenerated (pyknotic) nuclei. These cells were found in 25 of 30 mesothelioma samples (83%), 4 of 30 adenocarcinoma samples (13%) and 2 of 30 reactive samples (7%). The authors reported a sensitivity of 83%, specificity of 90%, positive predictive value of 81% and negative predictive value of 84%. When moderate or many such cells were present, specificity was 97% but sensitivity fell to 50%. All four positive adenocarcinomas were ovarian serous papillary adenocarcinomas. The authors concluded that the feature is highly specific and moderately sensitive for mesothelioma. They noted that the stain varies between laboratories, so their results may not be entirely representative.

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 study of diagnostic accuracy using archived cytology specimens, with two control groups
• Who was studied: 90 archived body cavity fluid specimens (pleural effusions, ascites, pericardial effusions) at the University of Chicago Hospital, accessioned January 2000 to November 2011. There were 30 histologically documented malignant mesotheliomas, all epithelioid type (24 pleural, 4 ascites, 2 pericardial). Controls were 30 adenocarcinomas (20 pleural, 10 ascites) and 30 cases of reactive mesothelial cells (18 pleural, 9 ascites, 3 pericardial).
• Exposure: Not studied. The article does not examine asbestos or any other exposure. The feature examined was the presence of parakeratotic-like cells (small, degenerated cells with orange-staining cytoplasm and pyknotic nuclei) on Papanicolaou-stained slides.
• Main results:
  • Parakeratotic-like cells were present in 25 of 30 mesothelioma cases (83%), 4 of 30 adenocarcinoma cases (13%) and 2 of 30 reactive mesothelial cell cases (7%).
  • For diagnosing mesothelioma, the presence of any parakeratotic-like cells had a reported sensitivity of 83%, specificity of 90%, positive predictive value of 81% and negative predictive value of 84%.
  • When moderate or many parakeratotic-like cells were present, specificity was 97% and sensitivity was 50%.
  • Among the 30 mesothelioma cases, 7 had many (more than 5 per slide), 8 had moderate (3 to 5 per slide) and 10 had rare (1 to 2 per slide) parakeratotic-like cells. Even when numerous, these cells were usually less than 1% of all cells.
  • The 5 mesothelioma cases without parakeratotic-like cells were either poorly cellular or had papillary structures.
  • All four positive adenocarcinoma cases were ovarian serous papillary adenocarcinomas, 4 of the 7 serous papillary cases (57%).
• The authors' conclusion: The authors concluded that the presence of parakeratotic-like cells in pleural effusion is a highly specific and moderately sensitive cytological feature for diagnosing mesothelioma in effusion specimens. They named serous papillary carcinoma as the major differential diagnosis.
• Limitations the authors state:
  • The Papanicolaou stain varies among laboratories, so the results may not be entirely representative. The authors said the finding may need further study in different laboratories.

Topics

Medical terms in this study, explained in our Lexicon: Mesothelioma, Neoplasm, Prognosis, Cytology, Adenocarcinoma, Reactive Mesothelial Hyperplasia, Pleural Effusion.

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