From a large number of clinical data, most anal fistulas are not cancerous, but only a few patients can develop malignant lesions for the following reasons: 1, long-term chronic inflammatory stimulation: the presence of long-term inflammation, making purulent matter or feces from the fistula, which stimulates abnormal cell proliferation, leading to malignant lesions. 2, bacterial infection: the long-term presence of bacteria in the fistula, especially Pseudomonas aeruginosa or tuberculosis infection, prolonged, 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. Therefore, anal fistula should be diagnosed and treated as early as possible to prevent the disease from becoming cancerous for a long time.