Anal fistula is a disease caused by a perianal abscess that is difficult to heal on its own without treatment. The consequence is a long-term flow of pus, secretions, and even feces from the fistula opening. The reason for this is the following: 1. long-term chronic inflammatory stimulation: the presence of long-term inflammation makes pus and feces discharge from the fistula, which stimulates abnormal cell proliferation and leads to malignant lesions. 2, bacterial infection: the long-term presence of bacteria in the fistula, especially Pseudomonas aeruginosa or tuberculosis infection, lingering, can lead to carcinogenesis. 3, drug stimulation: long-term use of a large number of various local topical drugs, often stimulating the local, leading to cancer. In short, anal fistula should be diagnosed and treated as early as possible to prevent the disease from becoming cancerous for a long time.