直肠癌和肛管癌是下消化道常见恶性肿瘤之一,该类肿瘤生长较缓慢,恶性程度中等,但因早期症状易被忽视,故临床所见大多系中、晚期病例,单纯手术切除, Rectal cancer and anal canal cancer are one of the common malignancies of the lower digestive tract. These tumors grow slowly and have a moderate degree of malignancy. However, because early symptoms are easily overlooked, most clinically seen cases are of intermediate or advanced stages and are surgically removed.