The majority of anal fistulas do not become cancerous after long-term clinical observation, but a very small number of anal fistulas can become cancerous. The reasons for this are: 1. long-term chronic inflammatory stimulation sometimes leads to abnormal tissue proliferation, and further development may lead to malignant transformation; 2. some bacterial infections, such as Pseudomonas aeruginosa or Mycobacterium tuberculosis infection, may lead to cancer; 3. long-term use of a large number of various topical drugs may lead to cancer. Although the incidence of cancer is low, it is more harmful once it occurs. Therefore, anal fistula should be treated in time to prevent the occurrence of cancer.