Cytopathological differential diagnosis between reactive mesothelial cells and metastatic adenocarcinoma in serous effusion

Objective To study the differential diagnosis between reactive mesothelial cells and adenocarcinoma in pleural and peritoneal effusion. Methods 48 cases of metastatic adenocarcinoma and 30 cases of reactive mesothelium in serous effusions were collected and prepared for HE stained smears and cell blocks.The morphology of two types of cells were observed and the expression of HBME-1,calretinin,E-cadherin,MOC-31 and BerEP4 were detected by immunocytochemical S-P method.Results The morphological characteristics of metastatic adenocarcinoma cells and reactive mesothelial cells in serous effusions were different and it was however difficult to distinguish well-differentiated adenocarcinomas from markedly hyperplastic reactive mesothelial cells,just based on the smear characteristics.The positive rates of HBME-1 and calretinin for reactive mesothelial cells were 86.7% and 76.7%,and the specificities were 95.8% and 100%,respectively.And the positive rates of MOC-31,E-cadherin and BerEp4 for metastatic adenocarcinomas were 70.8%,77.1% and 88.4%,and the specificities were 90%,93.3% and 93%,respectively.The differences between reactive mesothelial cells and adenocarcinoma were statistically significant(P0.05).Conclusions The combination of HE staining and immunocytochemistry on smear is great helpful for differential diagnosis of metastatic adenocarcinomas from mesothelial cells,especially adopting a panel of antibodies.It is very useful in differential diagnosis with antibody combination: HBME-1,calretinin,E-cadherin,MOC-31 and BerEP4.