For the clinicopathological characteristics analysis, patients with tumor located in rectum had a significantly lower PIK3CA mutation rate than other sites in colon and rectosigmoid transition zone (6.1% vs 15.1%, P<0.001) and proximal tumors appeared a higher PIK3CA mutation rate (19.8% vs 7.4%, P<0.001). The gene discussed is PIK3CA; the disease is neoplasm.