Value of E-cadherin and desmin immunohistochemistry in distinguishing metastatic adenocarcinoma from reactive mesothelial hyperplasia in serous effusion

Introduction One of the problems in studying serous effusion cytological samples is differentiation of reactive mesothelial cells from metastatic adenocarcinoma cells. Purpose The purpose of this research was to study the immunohistochemical diagnostic value of E-cadherin (ECAD) and desmin markers in differentiation of these two groups of cells. Patients and methods Seventy cases of serous effusions were examined as Papanicolaou-stained and Diff quick-stained smears, as well as paraffin-embedded cell blocks. Forty-three cases were diagnosed as metastatic adenocarcinoma and 27 cases were diagnosed as reactive mesothelial hyperplasia with typical cytomorphologic features. All the cases were studied for ECAD and desmin immunoreactivity. Results All cases of metastatic adenocarcinoma reacted to ECAD and only four cases reacted to desmin, whereas among the 27 cases of reactive mesothelial hyperplasia 25 cases were stained with desmin and only two cases were stained with ECAD. Conclusion The use of this short panel can be helpful for better differentiation of adenocarcinoma and reactive mesothelial hyperplasia in serous effusions, and it helps avoid overdiagnosis of metastatic adenocarcinoma because of the high sensitivity of ECAD.