[A Case of Carcinoma Associated with an Anal Fistula Repaired Using a Hatchet Flap after Neoadjuvant Chemoradiotherapy].

The patient was a 53-year-old man who complained of perianal pain. He had a 20-year history of an anal fistula. There was a 10 cm tumor with mucin-like discharge on the left side of the anus. His CEA level was high, at 7.3 ng/mL, and T2-weighted MRI revealed a multilocular cystic tumor with high signal intensity. The second biopsy result indicated mucinous adenocarcinoma. We performed neoadjuvant chemoradiotherapy. The chemotherapy regimen was TS-1 with radiation therapy, along with 4-port irradiation(50.4 Gy)of the primary tumor, located at the interior of the pelvis and inguinal lymph nodes. At the time of treatment completion, a partial response(PR)was observed, and a complete response(CR)was obtained after 6 months. We performed laparoscopic abdominoperineal resection. The large defect in the perianal skin and the pelvic cavity was repaired using a hatchet flap. The final diagnosis was confirmed as mucinous adenocarcinoma, pT4b, ly0, v0, N0, pPM0, pDM0, pRM0, pStage II . The patient was discharged 20 days after surgery. There is no indication of recurrence of the cancer after 1 year, and he continues to visit the outpatient clinic for regular follow-ups. Neoadjuvant chemoradiotherapy was effective in this case.