Small orangiophilic squamous-like cells: an underrecognized and useful morphological feature for the diagnosis of malignant mesothelioma in pleural effusion cytology

Our plain-English summary of Small orangiophilic squamous-like cells: an underrecognized and useful morphological feature for the diagnosis of malignant mesothelioma in pleural effusion cytology, by L. Chen, S.G. Caldero, S. Gmitro, et al (Cancer Cytopathology, 2014).

The study

• Authors: L. Chen, S.G. Caldero, S. Gmitro, M.L. Smith, G. De Petris, M.A. Zarka
• Journal: Cancer Cytopathology
• Published: 2014;122(1):70-5
• Cited by: 7 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: The cytological diagnosis of malignant mesothelioma (MM) on serous effusion is challenging due to significant morphologic overlap with reactive mesothelial cells and adenocarcinoma. One of the morphologic features of MM in effusion cytology, small orangiophilic squamous-like cells (SOSLC), has received little attention. To the best of the authors' knowledge, the current study is the first to assess the sensitivity and specificity of SOSLC in serous effusion specimens from histology-proven MM cases along with those of reactive mesothelial and adenocarcinoma cases.

Methods: A total of 130 cases of pleural (86 cases) and peritoneal (44 cases) effusion cytology cases (30 with histology-proven MM, 41 with adenocarcinoma, and 59 with reactive mesothelial cells) were studied. The presence or absence of SOSLC was recorded in each case.

Results: The cytological diagnoses of the 30 histology-proven MM cases included 1) atypical mesothelial cells, favor reactive (4 cases); 2) atypical mesothelial cells, suspicious for or cannot exclude mesothelioma (18 cases); and 3) positive for MM (8 cases). SOSLC were found in 10 of the 30 MM effusion cases (33.3%), 1 of the 41 adenocarcinoma cases (2.4%), and 5 of the 59 reactive mesothelial cell cases (8.5%). SOSLC were more likely to be present in MM effusions compared with either adenocarcinoma (P<.0001) or reactive mesothelial cell (P<.02) effusions. All 10 cases of MM with SOSLC were from pleural fluids. One case of peritoneal serous adenocarcinoma had SOSLC and 5 cases of reactive mesothelial cells in peritoneal fluid were found to have SOSLC.

Conclusions: Although not sensitive, the presence of SOSLC is quite specific for MM in pleural fluid cytology specimens. Finding this morphological feature in pleural fluid should alert the pathologist to a possible diagnosis of MM.

© 2013 American Cancer Society.

In plain English

This study asked whether a cell type seen under the microscope, called small orangiophilic squamous-like cells (SOSLC), helps pathologists recognize malignant mesothelioma in fluid drained from around the lungs (pleural fluid) or the abdomen (peritoneal fluid). The authors reviewed 130 fluid samples from the Cleveland Clinic and Mayo Clinic Arizona. Thirty came from patients whose mesothelioma was confirmed on tissue, all of the epithelioid type. Forty-one had adenocarcinoma and 59 had non-cancerous reactive mesothelial cells. Looking at the fluid alone, the original reports had called only 8 of the 30 mesothelioma cases positive for mesothelioma. SOSLC were found in 10 of 30 mesothelioma cases (33.3%), 1 of 41 adenocarcinoma cases (2.4%) and 5 of 59 reactive cases (8.5%). All 10 mesothelioma cases with SOSLC were pleural. In pleural fluid, SOSLC appeared in 10 of 25 mesothelioma cases (40%) and in none of the other pleural samples. All six non-mesothelioma cases with SOSLC were peritoneal. The authors concluded that SOSLC are not sensitive but are quite specific for mesothelioma in pleural fluid. They added that SOSLC alone are not enough to make the diagnosis. The article does not discuss 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: Diagnostic study reviewing archived effusion (body fluid) cytology slides from two hospital pathology databases for the presence or absence of SOSLC
• Who was studied: 130 effusion cytology cases (86 pleural, 44 peritoneal) from Cleveland Clinic and Mayo Clinic Arizona. These comprised 30 histology-proven malignant mesothelioma cases (25 pleural, 5 peritoneal; 2005 to 2012; all epithelioid type; median age 68), 41 adenocarcinoma cases and 59 reactive mesothelial cell cases (2009 to 2012).
• Exposure: No asbestos or fiber exposure was studied. The feature examined was the presence of small orangiophilic squamous-like cells (SOSLC) on Papanicolaou-stained smear and ThinPrep slides.
• Main results:
  • SOSLC were found in 10 of 30 malignant mesothelioma effusion cases (33.3%).
  • SOSLC were found in 1 of 41 adenocarcinoma cases (2.4%), an ovarian high-grade serous adenocarcinoma.
  • SOSLC were found in 5 of 59 reactive mesothelial cell cases (8.5% in the text; the table gives 8.4).
  • SOSLC were more common in mesothelioma effusions than in adenocarcinoma effusions (P less than .0001) or reactive mesothelial effusions (P less than .02).
  • In pleural effusions, SOSLC were present in 10 of 25 mesothelioma cases (40%) and in none of the adenocarcinoma or benign pleural effusions.
  • SOSLC were not found in any of the 5 peritoneal mesothelioma cases. All 6 non-mesothelioma cases with SOSLC were peritoneal fluids.
  • On the fluid samples, the original cytology diagnosis was positive for mesothelioma in only 8 of the 30 histology-proven mesothelioma cases.
• The authors' conclusion: The authors concluded that SOSLC are a helpful diagnostic feature for mesothelioma in pleural fluid and are quite specific there, but not in peritoneal fluid. They added that SOSLC alone are not sufficient to diagnose mesothelioma, but finding them may prompt appropriate workup.
• Limitations the authors state:
  • The authors stated that the presence of SOSLC alone is not sufficient to diagnose mesothelioma, and that other morphological features and ancillary studies may still be needed.
  • The authors could not determine the cell of origin of SOSLC, because the cells were very difficult to spot on immunocytochemical slides.
  • The authors stated that the cause of the link between SOSLC and mesothelioma in pleural fluid is unknown and beyond the scope of the study.

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: Malignant Mesothelioma, Pleural Effusion, Cytology, Reactive Mesothelial Cells, Adenocarcinoma, Histology, Mesothelial Cells, Mesothelioma.

Related studies

• Claudin-4 immunohistochemistry is highly effective in distinguishing adenocarcinoma from malignant mesothelioma in effusion cytology — V.Y. Jo, E.S. Cibas, et al. (2014)
• Loss of expression of BAP1 is a useful adjunct, which strongly supports the diagnosis of mesothelioma in effusion cytology — J. Andrici, A. Sheen, et al. (2015)
• The diagnostic utility of D2-40, calretinin, CK5/6, desmin and MOC-31 in the differentiation of mesothelioma from adenocarcinoma in pleural effusion cytology — T.S. Hyun, M. Barnes, et al. (2012)
• Cytological differential diagnosis among adenocarcinoma, epithelial mesothelioma, and reactive mesothelial cells in serous effusions by immunocytochemistry — X.Y. Su, G.D. Li, et al. (2011)
• Cytomorphological features of metastatic squamous cell carcinoma in serous effusions — C.C. Huang, C.W. Michael (2014)
• EZH2, a unique marker of malignancy in effusion cytology — H. Jiang, R. Gupta, et al. (2014)

Browse more research in Cancer Cytopathology, or return to medical research.