Role of HEG1 and Claudin-4 Immunohistochemistry in the Differential Diagnosis of Lung Adenocarcinoma from Malignant Mesothelioma in Pleural Effusion Cytology

Our plain-English summary of Role of HEG1 and Claudin-4 Immunohistochemistry in the Differential Diagnosis of Lung Adenocarcinoma from Malignant Mesothelioma in Pleural Effusion Cytology, by A.E. Abdelrahman, F.A. Elbadry, T.R. Ibrahim, et al (Türk Patoloji Dergisi, 2025).

The study

• Authors: A.E. Abdelrahman, F.A. Elbadry, T.R. Ibrahim, M.A. Alabiad, M. Awad
• Journal: Türk Patoloji Dergisi
• Published: 2025;41(2):42-50
• Read it: PubMed · Publisher · Free full text

Abstract

Objective: Cytological examination of pleural effusion is minimally invasive and low risk but faces challenges due to the lack of architectural features, low cell counts, and overlapping characteristics among reactive mesothelial cells (RMCs), carcinoma cells, and malignant epithelioid mesothelioma (MPM) cells. The aim of this was study to detect the diagnostic accuracy of the expression of HEG1 and Claudin-4 in distinguishing malignant mesothelioma from lung adenocarcinoma in pleural effusion.

Material And Methods: The present study was carried out on 84 cases of pleural effusion. Sixty-four representative cell blocks of the studied malignant cases and twenty control cases were stained with HEG1 and Claudin-4 immunostaining, and the results were recorded.

Results: Positive membranous HEG1 immunoexpression was found in 95% of RMCs in benign effusions. Also, positive membranous HEG1 immunoexpression was found in 96% of cases of MPM, and only 2.6% of lung adenocarcinoma cases. There was a statistically significant difference between benign effusion with RMCs and lung adenocarcinoma immunoreactivity. There was a highly statistically significant difference between HEG1 immunoexpression in MPM and lung adenocarcinoma. On the other hand, all cases of benign effusions and all MPM cases had negative Claudin-4 immunoexpression while positive membranous Claudin-4 immunoexpression was found in 94.9% of lung adenocarcinoma cases. There was a statistically significant difference in immunoexpression of Claudin-4 between benign effusion and lung adenocarcinoma. There was a statistically significant difference in the immunoexpression of Claudin-4 between MPM and lung adenocarcinoma.

Conclusion: HEG1 and Claudin-4 IHC staining is extremely valuable in the differential diagnosis between reactive or malignant mesothelial cells and adenocarcinoma in pleural effusion.

In plain English

This study tested whether two laboratory stains, HEG1 and Claudin-4, could tell malignant mesothelioma apart from lung adenocarcinoma in fluid that collects around the lungs (pleural effusion). The authors used 84 pleural effusion samples collected between December 2021 and May 2023. There were 25 malignant pleural mesotheliomas, 39 lung adenocarcinomas, and 20 benign effusions containing reactive mesothelial cells. Surgical biopsy findings served as the reference standard. Claudin-4 was negative in all 25 mesotheliomas and all 20 benign samples. It was positive in 37 of 39 adenocarcinomas (94.9%). HEG1 was positive in 24 of 25 mesotheliomas (96%) and in 19 of 20 benign samples (95%), and negative in 38 of 39 adenocarcinomas (97.4%). Used together, the two stains identified mesothelioma with 96% sensitivity (95% confidence interval 79.648 to 99.899) and 97.436% specificity (95% confidence interval 86.524 to 99.935). The authors stated that HEG1 could not separate mesothelioma from benign reactive cells. They concluded that the two stains together are particularly useful for separating reactive or malignant mesothelial cells from adenocarcinoma. It did not examine 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 accuracy study of HEG1 and Claudin-4 immunostaining on pleural effusion cell blocks, with surgical biopsy examination as the reference standard
• Who was studied: 84 pleural effusion samples collected between December 2021 and May 2023 from departments of chest and cardiothoracic surgery: 64 malignant effusions (25 malignant pleural mesothelioma, 39 lung adenocarcinoma) and 20 benign effusions with reactive mesothelial cells
• Exposure: No asbestos or other environmental exposure was studied. The 'exposure' was immunostaining of cell blocks with HEG1 (rabbit polyclonal antibody, Bioss) and Claudin-4 (rabbit polyclonal antibody, Lab Vision/Thermo Scientific).
• Main results:
  • Claudin-4 was negative in 25 of 25 (100%) malignant pleural mesothelioma cases and in all 20 benign effusions with reactive mesothelial cells.
  • Claudin-4 was positive in 37 of 39 (94.9%) lung adenocarcinoma cases.
  • HEG1 was positive in 24 of 25 (96%) mesothelioma cases.
  • HEG1 was negative in 38 of 39 (97.4%) lung adenocarcinoma cases.
  • HEG1 was positive in 19 of 20 (95%) benign effusions with reactive mesothelial cells.
  • The authors stated that HEG1 could not differentiate mesothelioma from benign reactive mesothelial cells.
  • The combined pattern of negative Claudin-4 and positive HEG1 had a sensitivity of 96% (95% CI 79.648 to 99.899) for diagnosing mesothelioma.
  • The same mesothelioma pattern had a specificity of 97.436% (95% CI 86.524 to 99.935) and an accuracy of 96.875% (95% CI 89.163 to 99.619).
  • For diagnosing lung adenocarcinoma, the combined pattern had a sensitivity of 94.872% (95% CI 82.676 to 99.373).
  • The lung adenocarcinoma pattern had a specificity of 100% (95% CI 86.281 to 100).
• The authors' conclusion: The authors concluded that HEG1 and Claudin-4 staining together are particularly useful for differentiating reactive or malignant mesothelial cells from adenocarcinoma in pleural effusion.

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: HEG1, Claudin-4, Immunohistochemistry, Differential Diagnosis, Lung Adenocarcinoma, Mesothelioma, Pleural Effusion, Cytology.

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)
• Utility of Claudin-4 versus BerEP4 and B72.3 in pleural fluids with metastatic lung adenocarcinoma — A. Patel, A.C. Borczuk, et al. (2020)
• 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)
• Immunocytochemical utility of claudin-4 versus those of Ber-EP4 and MOC-31 in effusion cytology — T. Oda, S. Ogata, et al. (2016)
• Claudin-4 immunohistochemistry is a useful pan-carcinoma marker for serous effusion specimens — M. Vojtek, M.D. Walsh, et al. (2019)
• Diagnostic Value of Claudin-4 and EZH2 Immunohistochemistry in Effusion Cytology — A. Elhosainy, M.M.A. Hafez, et al. (2022)

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