Implantation of a benign rectal villous adenoma in the surgical track after transsphincteric excision. Report of a case.

A 56-year-old male patient underwent excision of a rectal villous adenoma by a transsphincteric approach. Six years after surgery, an extrarectal mucinous mass was noted, which, on biopsy, had histologic features of implantation of benign villous adenoma within the operative scar. For medical reasons, surgery was avoided and the lesion enlarged until symptoms necessitated rectal excision five years later. Histologic examination of the resected mucinous tumor supported an origin from implanted adenomatous epithelium. This is apparently the first description of implantation of an adenoma in the surgical track. Care should be taken during transsphincteric and transsacral excision of rectal adenomas to prevent implantation at the time of surgery.