A case of rectosigmoid cancer metastasizing to a fistula in ano.

We herein report a case of rectosigmoid cancer metastasizing to a fistula in ano. A 53-year-old man complaining of anal bleeding consulted another hospital. He had been suffering from an anal fistula since 7 years. On the left upper side of the skin surface around the anus a fistula end was seen as a hole that tunneled down into the back passage, although no hard tumor was palpable on the hole. Complete colonoscopy revealed an ulcerative tumor in the rectosigmoid colon. On 5 February 2004, anterior resection and lymphadenectomy was performed. The post-operative pathological diagnosis was rectosigmoid cancer, Type 2, T2, N0, M0, stage II. The anal fistula was a simple type and mucinous discharge was not observed. On 23 February 2004, coring out the anal fistula was performed by the former hospital. Pathological diagnosis of the excised fistula revealed well-differentiated adenocarcinoma; identical to the colon tumor. Immunohistochemical staining of these two lesions were negative for (CK) 7 but staining with CK20 revealed some stained tumor cells in two lesions. We diagnosed this tumor as metastatic adenocarcinoma from a rectosigmoid cancer. Recurrent lesions were not seen during the first year after the first operation.