What is anal cancer? Most anal cancers occur on the skin of the anal canal or anal verge and are mostly squamous epithelial carcinomas, with a few basal cell carcinomas. Cancer that grows at the dentate line is anal canal cancer; cancer that grows below the dentate line is perianal cancer or anal verge cancer. Anal canal cancers are more common in women and perianal cancers are more common in men. Squamous cell carcinoma mostly occurs in anal canal and perianal area, which is caused by squamous epithelium of anal canal and perianal area, often caused by anal fistula, hemorrhoids, surgical scars, warts, suppurative sweat gland and submerged hair cysts with long-term chronic stimulation injury. Xin Xuezhi, Department of Anus and Intestines, Thousand Buddha Mountain Hospital, Shandong Province, China The cause of anal cancer is still unclear, and the literature introduces that it is related to the following factors: chronic inflammation, such as anal fistula, anal fissure, suppurative sweating inflammation, anal warts, anal leukoplakia, sacrococcygeal teratoma and so on, which can be regarded as pre-cancerous lesions. Due to chronic long-term stimulation, it causes degenerative changes of cells and loses normal re-differentiation ability, resulting in cancerous transformation. Squamous carcinoma invades perineum, scrotum, labia and inguinal lymph nodes. The transmission pathway is by venous metastasis. As anal canal cancer is poorly differentiated, less keratinized and highly malignant, it often invades the perirectal and mesenteric lymph nodes along the intestinal lymphatic vessels upward, with more early metastasis and poor prognosis. Perianal cancer is better differentiated, with more keratinization, low malignancy, rare metastasis, and good prognosis after surgery. How should anal cancer be treated? Surgery: Surgical treatment depends on the tumor site, whether there is invasion of sphincter and whether there is lymph node metastasis in groin. Local excision: if the perianal cancer below the dentate line does not exceed 1/3 of the perianal area and does not invade the sphincter muscle, extensive local excision is mostly feasible. If the tumor diameter is less than 2cm, with good activity and low deterioration, because perianal cancer rarely metastasizes to the lymph nodes next to the rectum and mesenteric blood vessels, at least 2.5cm of skin outside the edge of the tumor should be resected circumferentially, and part of muscle should be resected if necessary, and the skin can not be sutured and skin grafting should be carried out, and the prognosis is better, and the patient can survive for more than 5 years. Local excision with high-frequency electric knife can obtain a margin free of tumor cells.