The introduction of total mesorectal excision and the use of neoadjuvant therapy has led to improved prognosis of rectal cancer. Circumferential resection margin(CRM) is one of the main prognostic factors. Positive CRM is associated with adverse prognosis. It is of clinical significance to clarify different patterns of CRM involvement, the exact definitions, and associated factors. TME quality assessment and accurate determination of CRM involvement are crucial in the pathologic examination of rectal cancer. Extended abdominoperineal resection during which the levator muscles are resected en bloc with the anus and lower rectum may be superior than conventional abdominoperineal resection (APR) in terms of obtaining a negative CRM.