The cytologic application of carcinoembryonic antigen for the discrimination of malignant from benign serous effusions.

In an attempt to diminish false cytologic diagnosis in discriminating between benign and malignant effusions, the value of intracellular carcinoembryonic antigen (CEA) was estimated in cytologic smears of effusions using a modified immunoperoxidase technique. CEA serum level was estimated by radioimmunoassay technique. In this study we included a group of 42 patients, 23 with a malignant and 19 with a benign effusion. CEA in cells of effusions was positive and useful for confirming malignancy in 65% of malignant effusions. The percentage increased to 83% with the combination of the results of positive CEA in cells and serum. Cytology was positive for malignancy in 16 of the 23 (70%) malignant cases. CEA in cells of benign effusions was negative in 84% and cytology in 100%. It is concluded that intracellular CEA estimation, when combined with CEA estimation in serum, improves the discriminating range of cytology for differentiating malignant and benign effusions.