The use of carcinoembryonic antigen for identification of human tumor cells in malignant effusions.

A specific anti-carcinoembryonic antigen (CEA) antiserum was used to identify CEA-positive tumor cells in peritoneal and pleural effusions obtained from patients with various malignant neoplasia. In 7 out of 10 fluids in which tumor cells were detected by cytological examinations, cytoplasmic CEA-positive cells were also detected by an indirect immunofluorescence test. In addition, out of 11 fluid samples cytologically negative for tumor cells, CEA-positive cells were found in 8 cases. When both staining for cytoplasmic CEA and soluble fluid CEA levels were considered in combination, 81% of the samples were found to be positive by either one or both of these markers, whereas only 54% were positive by using cytological criteria. The data suggest that CEA marker may be used to identify tumor cells and to assess malignancy in pleural and peritoneal effusions in patients with certain types of cancer. The CEA marker was also used for identifying tumor cells grown in tissue cultures and for separating viable CEA-positive and CEA-negative cells from a mixed cell population using the fluorescence-activated cell sorter.