DETECTION OF FREE MALIGNANT-CELLS IN THE PERITONEAL-CAVITY BEFORE ANDAFTER RESECTION OF COLORECTAL-CANCER

PURPOSE: This study was designed to select the best monoclonal antibod y to stain malignant cells in peritoneal wash fluid, and to investigat e the incidence of free malignant cells in preresection and postresect ion colorectal cancer peritoneal washings using a combination of conve ntional cytology and immunocytochemistry. METHODS: Peritoneal washings were taken from 35 consecutive patients undergoing colorectal cancer resection. RESULTS: Malignant cells were isolated on a density gradien t and identified by conventional cytology and an indirect immunoperoxi dase stain, Malignant cells were identified in peritoneal washings fro m 15 patients (preresection only n = 3, postresection only n = 4 both n = 8). The origin of free malignant peritoneal cells in 11 preresecti on-positive washings must be the serosa. The origin of these cells in the four postresection-positive patients is uncertain: serosal and lum inal spillage were considered unlikely and no circulating cells were f ound in the mesenteric vessels near the tumor. CONCLUSION: Tumor cells may have leaked out from lymphatics cut during the dissection.