Anal canal cancer refers to malignant tumors originated from or mainly located in anal canal, and anal canal and perianal canal tumors are relatively rare in clinic, accounting for less than 2% of colorectal and rectal tumors. Anal canal cancer is prevalent in middle-aged and old-aged people, and the incidence rate of women is slightly higher than that of men; clinical symptoms are mainly hemorrhage and pain. Localization can involve vagina, rectum, prostate, urethra and surrounding soft tissues; lymphatic metastasis is an important metastatic mode of anal canal cancer, which usually occurs in inguinal lymph nodes first. Early diagnosis mainly relies on anal canal and rectal fingerprinting and biopsy. Ultrasound and MRI in anal canal can help preoperative staging, guide the choice of treatment plan and evaluate the prognosis: I. Surgical treatment 1. Transabdominal perineal colectomy (Miles operation): with the affirmation of the effect of radiotherapy and chemotherapy on the treatment of anal canal cancer in recent years, expanded Miles operation is no longer taken as the first choice of treatment, especially in early stage of anal canal cancer, and the surgical treatment is performed as an auxiliary treatment. However, for clinical stage T3 and T4 anal canal cancer, NCCN guidelines still recommend Miles operation as the main treatment modality, with preoperative or postoperative radiotherapy. Inguinal lymph node dissection: the first station of lymphatic transfer from anal canal cancer to the lower part of the body reaches the inguinal lymph nodes, and the metastasis rate is 8.2%～40.5%. In recent years, it has been recognized that prophylactic inguinal lymph node dissection cannot improve the 5-year survival rate and reduce the recurrence rate, but when inguinal lymph node metastasis is found in the follow-up after Miles operation, inguinal lymph node dissection can also get satisfactory results. Therefore, the NCCN guideline recommends regular and close review and follow-up after radical surgery for anal canal cancer, and inguinal lymph node palpation and imaging examination should be performed every 3-6 months within 5 years after surgery, and inguinal lymph node dissection should be performed in time if lymph node metastasis is confirmed. 3.Local excision: local excision can be radical or palliative; in NCCN guidelines, local excision is recommended for stage I squamous cell carcinoma with primary tumor ≤2cm, superficial location without deep invasion, without any sign of metastasis, and well-differentiated cells as confirmed by pathology; the excision scope should be at least 2.5cm of the skin outside the margins and part of the muscle, and the function of sphincter should be preserved. Palliative local excision can also be applied to patients whose systemic condition cannot tolerate transabdominal perineal combined excision, as well as those with residual lesions after radiotherapy, and sometimes it is also used for patients with local recurrence. The purpose of palliative local excision is to remove the lesions seen by the naked eye, and radiotherapy is often needed after the operation. With the development of equipment and technology, in-depth theoretical research and change of concepts, radiotherapy has gradually been emphasized in the treatment measures of anal canal cancer and has replaced traditional surgery as the first choice. Some scholars advocate that the addition of chemotherapy can increase sensitivity, less radiotherapy dose, and have systemic therapeutic effect to eliminate tiny lesions. The radiotherapy and chemotherapy regimen recommended by NCCN guideline is: for anal canal cancer without metastasis, 5-fu/capecitabine + mitomycin with radiotherapy, total amount of radiotherapy is 45Gy/5 weeks, irradiation scope includes inguinal area, and then external irradiation after 6 weeks of rest, with an enhancement dose of 15Gy/6 times or intertissue irradiation with radionuclide 192Ir, total amount of 25Gy; for anal canal cancer that has metastasis, chemotherapy can be used to increase sensitivity and reduce the systemic treatment effect. of anal canal cancer, the chemotherapy regimen was cisplatin + 5-fu,. The total amount of radiotherapy is 54-59Gy/6-7.5 weeks. Early stage patients can be treated with local excision and postoperative radiotherapy; T3 and T4 patients can be treated with surgery and preoperative or postoperative radiotherapy; those who are not suitable for surgery can only be treated with radiotherapy. Treatment of adenocarcinoma of anal canal Adenocarcinoma of anal canal is a malignant tumor originated from anal glands, the incidence rate is very low, the incidence rate of male is higher than that of female, and the local recurrence and metastasis rate is higher than that of squamous cell carcinoma of anal canal. Treatment is by Miles surgery combined with postoperative radiotherapy and 5-FU-based chemotherapy, with a 5-year survival rate of approximately 35%. Prognosis The factors affecting the prognosis of anal canal cancer are mainly the stage of tumor, especially the depth of tumor infiltration has a great influence on the 5-year survival rate. 5-year survival rate of T1 and T2 patients can reach 70%-100%, while that of T3 and T4 patients is only 10%-40%, and if the tumor invades the muscle or the soft tissues outside the sphincter, the rate of recurrence is up to more than 60% after surgery. Regional lymph node metastasis is an even worse prognostic factor, especially when inguinal lymph nodes are found at the same time as the primary tumor. The degree of differentiation of the tumor is related to the prognosis, the 5-year survival rate of well-differentiated patients without regional lymph node metastasis reaches 75%; the poorly differentiated patients with regional lymph node metastasis are only 24%. The histologic type is also obviously related to the prognosis. Most anal canal cancers are squamous cell carcinomas, which have a better prognosis than adenocarcinomas and melanomas. Comprehensive treatment has better prognosis than single treatment. 5-year survival rate of patients after combined radiotherapy and chemotherapy-based comprehensive treatment in foreign countries has increased to 65%～80%, while only 45%～70% in pure surgical treatment, and the local recurrence rate of comprehensive treatment is lower than that of pure surgical treatment by about 20%.