Operative findings. (a) The oral edge of the tumor located further from the anal verge than expected with the slack condition of the sphincter (arrow). (b) The hemispherical incision was made from one mid-ischial tuberosity to the other with the apex approximately 2 cm above the anus. (c) The central tendon was transected after tunneling beneath the superficial transverse perineal muscle. (d) The recto-urethral muscle was transected with insertion of an index finger into the rectum to ascertain the tumor.