Significance of immunocytochemical expression of E-cadherin, N-cadherin and CD44 in serous effusions using liquid-based cytology

OBJECTIVE: To assess the diagnostic utility of E-cadherin (E-cad), N-cadherin (N-cad) and CD44 to discriminate adenocarcinoma cells from benign and malignant mesothelial cells in body cavity fluids and to clarify the origin of cancer cells. STUDY DESIGN: A total of 120 ThinPrep (Cytyc Corp., Boxborough, Massachusetts, U.S.A.) cytologic specimens of serous effusions, which included 22 cases of reactive mesothelium, 6 cases of malignant mesothelioma and 92 cases of metastatic adenocarcinoma from various sites, were immunostained for E-cad, N-cad and CD44. RESULTS: Eighty-three of 92 metastatic adenocarcinomas (90.21%) expressed E-cad, while 1 of 6 malignant mesotheliomas and 1 of 22 cases of reactive mesothelium were positive for E-cad. All 6 cases of mesothelioma expressed N-cad, whereas most cases of metastatic adenocarcinomas were negative. CD44 immunoreactivity was seen in 18 of 22 (81.81%) benign effusions and in 21 of 92 (22.82%) metastatic adenocarcinomas. CONCLUSION: The combination of E-cad, N-cad and CD44 appears to be a useful panel for distinguishing metastatic adenocarcinoma, mesothelioma and reactive mesothelium and also for clarifying the exact histogenetic origin of cancer cells. This is of great importance in a few otherwise-insoluble cases because of differences in tumor treatment and prognosis.