直肠癌发病率不断升高,病因还不清楚,虽与遗传、腺瘤和慢性炎症有关系,但肠内拟杆菌和饮食是重要因素。组织学分为腺癌、粘液癌、印戒细胞癌、鳞状上皮癌、腺鳞癌、未分化癌和未分类癌。大体形态分型:菜化型或息肉样癌不常有较多的肠壁浸润,生长迅速,转移较晚,予后较好。溃疡型转移较早。环型或狭窄型沿纵向扩展,可 The incidence of rectal cancer is increasing, and the cause is not yet clear. Although it is related to heredity, adenoma and chronic inflammation, Bacteroides intestine and diet are important factors. Histology is classified into adenocarcinoma, mucinous carcinoma, signet-ring cell carcinoma, squamous cell carcinoma, adenosquamous carcinoma, undifferentiated carcinoma, and unclassified carcinoma. General morphology classification: Vegetable-type or polypoid carcinoma does not often have more intestinal wall infiltration, rapid growth, late transfer, and better after giving. The ulcer type metastasis is earlier. Ring or narrow type extends in the vertical direction