Anal lesion resulting from implantation of viable tumour cells in a pre-existing anal fistula. A case report.

Colorectal cancer exfoliates cancer cells into the lumen of the bowel, and possibly, raw bowel mucosa should provide a good medium for the exfoliated cancer cells. We report an extremely rare case of a sigmoid carcinoma metastasizing to a low fistula in ano. The patient was operated on for a fistula in ano. Biopsy demonstrated a moderate differentiated adenocarcinoma. Thereafter, sigmoidoscopy revealed an intraluminal mass at the sigmoid colon. The patient subsequently underwent abdominoperineal resection of the sigmoid colon and rectum. In conclusion, surgeons should be aware of the possibility of cancer spread incidence, distally beyond the initial site by exfoliated cancer cells into the lumen of the bowel.