Flow cytometric identification of cancer cells in effusions with Ca1 monoclonal antibody

The fluorescence of cells from 42 pleural and peritoneal effusions stained with Ca1 monoclonal antibody (Ca1MA) was studied by flow cytometry. In 14 of 17 malignant effusions a significantly higher intensity of fluorescence was observed in samples exposed to Ca1MA when compared with controls. There was no increase of fluorescence intensity in 25 benign effusions. The method failed in three malignant effusions: one due to endometrial carcinoma and two to malignant lymphoma. The sensitivity of the method was tested in experimental samples with a known percentage of malignant cells. The positive fluorescence with Ca1MA was detected in samples containing 0.1% of carcinoma cells. Flow cytometry with Ca1MA can be a relatively simple method of identification of malignant cells in effusions.