Use of Panel of Markers in Serous Effusion to Distinguish Reactive Mesothelial Cells from Adenocarcinoma

Although cytological examination helps in diagnosis of malignancy in serous effusion, at times it is difficult to differentiate atypical reactive mesothelial cells from adenocarcinoma (AC) cells. To resolve this problem, various ancillary methods have been used. Immunocytochemistry (ICC) is one such commonly used technique in which various panel of antibodies has been tried. Unfortunately, so far no unique marker is available to solve this issue. Hence, the present study evaluates the efficacy of four antibody panel comprising of MOC-31, epithelial membrane antigen (EMA), calretinin (CAL), and mesothelin (MES) to solve this problem.

Forty-two cases suspected of malignant effusion in pleural/peritoneal fluid and 42 cases of reactive effusion were included. Cytospin smears were prepared and stained with Giemsa stain for cytomorphological diagnosis. Cytospin smears and cell blocks were made forICC. ICC for MOC-31, EMA, CAL, and MES was performed.

Among the suspected malignant effusion cases, 30 cases were AC and 12 cases were suspicious for malignancy by cytomorphology. MOC31 demonstrated 100% sensitivity (Sn) and 95.24% specificity (Sp), and EMA had 88.1% Sn and 92.86% Sp for AC cases. CAL demonstrated 100% and 97.62%, and MES 97.62% and 88.1% Sn and Sp in reactive mesothelial cells, respectively.

In conclusion, combination of MOC-31 and CAL as a limited panel will be helpful in giving an appropriate diagnosis in difficult cases and thereby, help in patient management. In addition, ICC on cytospin smears gave results similar to cell blocks, and if standardised cytospin is simple technique to perform, unlike cell blocks.