CEA, ZGM and EMA localization in cells of pleural and peritoneal effusion: a preliminary study

Carcinoembryonic antigen (CEA), the zinc glycinate marker (ZGM) and epithelial membrane antigen (EMA) have been described as epithelial or tumour markers of varying specificity. These antigens were studied by immunoperoxidase localization in selected cell blocks of 62 pleural or peritoneal effusions and compared to cytological findings and review of the clinical records. By cytological criteria, 25 of the cell blocks were positive for malignancy, 30 negative, and 7 inconclusive. CEA, ZGM, and EMA by immunoperoxidase staining were localized on the cell surface and often in the cytoplasm of malignant cells, in 11/25 (44 per cent), 17/25 (68 per cent) and 22/25 (88 per cent) of the positive cell blocks respectively. Ten (40 per cent) of these cases were positive for all three antigens, 7 (28 per cent) for two, and 6 (24 per cent) for one. Of the 7 cases which were inconclusive on routine cytological reporting, 5 were positive for at least one marker. In 3 of the 5 a diagnosis of malignancy was confirmed, and in the other two was strongly suspected as malignant on clinical grounds. Macrophages were sometimes positive for one or more markers (but showed cytoplasmic staining only) and mesothelial cells in some cases stained positively for EMA but were always negative for CEA and ZGM. Localization of the 3 antigens in cells of malignant effusions was compared with their localization in the primary tumours in 9 cases. Localization corresponded for CEA in 7 of 9 cases, for EMA in 8 of 8 an for ZGM in only 2 of 9. Effusion fluid levels for CEA were compared with the cytological and immunocytochemical findings in 30 cases. Mucin stains performed on the cell blocks were also compared with the immunoperoxidase findings.