The incidence of positive peritoneal cytology in colon cancer: a prospective randomized blinded trial

Many investigators have attempted to explain the suspected increased incidence of port site metastasis in patients undergoing laparoscopic colorectal resections for cancer with animal models in which cancer is simulated by injection of a tumor slurry into the peritoneal cavity. This approach makes the basic assumption that all patients with colorectal malignancies have viable cancer cells freely circulating within the peritoneal cavity. Recent reports in open colorectal resections have conflicting results. Some suggest that the true incidence is negligible and related to advanced-stage cancers whereas others implicate a much higher incidence. We initiated a prospective blinded trial to establish the true incidence of malignant peritoneal cytology in colorectal cancer. One hundred eight consecutive colon resections underwent conventional peritoneal cytologic evaluation. The patients included those with inflammatory conditions of the colon as well as malignant disease. The cytopathologist was blinded as to the indications for surgery as well as the final pathology result. In only one case--stage IV rectal cancer with peritoneal carcinomatosis--was the cytologic specimen positive. Malignant cytology appears to be an infrequent occurrence and is restricted to advanced-stage cancer.