Abstract
The patient was a 63-years-old man who presented with fever, pain, and a tumor (2×3cm) in left around the anus. Episodes of discharge from the tumor had continued for 12 years and this suggested the presence of an anal fistula. Biopsy showed well-differentiated squamous cell carcinoma. We diagnosed carcinoma associated with anal fistula and performed rectal amputation. Histopathological examination showed cancer pearl formation and the deposition of melanin. There were no fistulas between the tumor and the rectal mucosa. Therefore, we diagnosed the skin carcinoma. The patient is now alive and has not shown recurrence. Carcinoma associated with anal fistula is a rare cancer found in patients with long-term fistulae. Clinical diagnostic criteria are used for diagnosis. Our case filled the criteria but was actually derived from skin. In cases where it is difficult to prove the presence of an anal fistula in preoperative images, skin cancer should be considered and adequate surgical procedures should be planned.
