A Case of Squamous Cell Carcinoma of the Anal Canal with a Perianal Abscess

A 72-year-old female patient was referred to our department because she felt pain at the anus with pus discharge. Physical examination revealed a tumor on the left side of the anus, and a subcutaneous induration near the tumor. Abdominal CT scan revealed an irregularly shaped tumor with abscess formation. There were no enlarged lymph nodes or distant metastasis. Anal canal carcinoma (cStage Ⅱ) with a complication of perianal abscess was suspected, so we performed surgical incision and drainage. A biopsy of the tumor led to the diagnosis of squamous cell carcinoma. However, because surgical drainage alone was not effective for treatment of the abscess, colostomy of the sigmoid colon was carried out 14 days after admission. After chemoradiation therapy (5-FU 800 mg/m2/day on days 1-4 and 29-32, mitomycin C [MMC] 10 mg/m2 on days 1 and 29, and radiation with a total dose 54 Gy), the tumor disappeared completely, considered to be a complete response. Twenty months after chemoradiation, there were no signs of recurrence.