Diagnostic Value of the EZH2 Immunomarker in Malignant Effusion Cytology

Acta Cytol. 2020;64(3):248-255. doi: 10.1159/000501406. Epub 2019 Jul 26.

Abstract

Background: Differentiating reactive mesothelial cells from metastatic carcinoma in effusion cytology is a challenging task. The application of at least 4 monoclonal antibodies including 2 epithelial markers (Ber-EP4, MOC-31, CEA, or B72.3) and 2 mesothelial markers (calretinin, WT-1, CK5/6, or HBME-1) are often useful in this distinction; however, it is not readily available in many resource-limited developing countries. Aberrant immunoexpression of enhancer of zeste homolog 2 (EZH2), a transcriptional repressor involved in cancer progression, is observed widely in various malignancy. In this study, we evaluate the diagnostic value of EZH2 as a single reliable immunomarker for malignancy in effusion samples.

Methods: A total of 108 pleural, peritoneal, and pericardial effusions/washings diagnosed as unequivocally reactive (n = 41) and metastatic carcinoma (n = 67) by cytomorphology over 18 months were reviewed. Among the metastatic carcinoma cases, 54 were adenocarcinoma and others were squamous cell carcinoma (n = 1), carcinosarcoma (n = 1), and carcinoma of undefined histological subtypes (n = 11). Cell block sections were immunostained by EZH2 (Cell Marque, USA). The percentages of EZH2-immunolabeled cells over the total cells of interest were calculated. Receiver operating characteristic (ROC) curve analysis was performed to determine the optimal cut-off score to define EZH2 immunopositivity.

Results: A threshold of 8% EZH2-immunolabeled cells allows distinction between malignant and reactive mesothelial cells, with 95.5% sensitivity, 100% specificity, 100% positive predictive value, and 93.2% negative predictive value (p < 0.0001). The area under the curve was 0.988.

Conclusion: EZH2 is a promising diagnostic biomarker for malignancy in effusion cytology which is inexpensive yet trustworthy and could potentially be used routinely in countries under considerable economic constraints.

Keywords: Effusion cytology; Enhancer of zeste homolog 2; Immunocytochemistry; Metastatic carcinoma; Reactive mesothelial cells.

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Ascitic Fluid / chemistry
  • Ascitic Fluid / pathology*
  • Biomarkers, Tumor / analysis*
  • Carcinoma / complications
  • Carcinoma / diagnosis*
  • Cytodiagnosis / methods
  • Enhancer of Zeste Homolog 2 Protein / analysis*
  • Female
  • Humans
  • Immunohistochemistry / methods
  • Male
  • Middle Aged
  • Pericardial Effusion / diagnosis*
  • Pericardial Effusion / etiology
  • Pleural Effusion, Malignant / diagnosis*
  • Pleural Effusion, Malignant / etiology
  • Retrospective Studies
  • Young Adult

Substances

  • Biomarkers, Tumor
  • EZH2 protein, human
  • Enhancer of Zeste Homolog 2 Protein