Immunocytochemical panel for distinguishing between carcinoma and reactive mesothelial cells in body cavity fluids

The morphological evaluation of cytological specimens from body cavity fluids presents difficulties in the differential diagnosis between benign reactive mesothelial (RM) cells and adenocarcinoma (AC) or malignant mesothelioma (MM). The aim of our study was to investigate whether a panel of five different antibodies can offer reliable markers in the differential diagnosis of RM, AC, and MM in serous effusions. A total of 134 cytological specimens of serous effusions from 80 ACs, 50 RMs, and 4 MMs, previously stained with Papanicolaou stain, were selected retrospectively from our files and stained with anti-human mesothelial cell (HBME-1), calretinin, epithelial specific antigen (MOC-31), Ber-EP4, and BG8. Statistical significance was found with HBME-1, calretinin, MOC-31, anti-human epithelial antigen (Ber-EP4), and blood group related antigen (BG8) when comparing AC vs. any type of mesothelial proliferation (MM or RM). The sensitivity of HBME-1 and calretinin for mesothelial cells was 98 and 100%, respectively, and the specificity was 71 and 80%, respectively. Both antibodies stained reactive mesothelial as well as MM cells, with calretinin showing a stronger intensity of immunostaining. The sensitivity of the stain for AC was 86.25% for MOC-31, 77.5% for Ber-EP4, and 67.5% for BG8, and, when combined, the sensitivity was 100%. Our data suggest that immunocytochemical studies performed on Papanicolaou-stained cytological smears with HBME-1, calretinin, MOC-31, Ber-EP4, and BG8 proved to be useful in the differentiation between metastatic AC and mesothelial proliferation. Probably, calretinin is a more preferred marker for mesothelial cells as evidenced by a more intense staining reaction.