Adequate length of the surgical distal resection margin in rectal cancer: from the viewpoint of pathological findings.

BACKGROUND Previous studies have not identified how to determine the optimal distal margin in rectal cancer based on histopathological diagnosis. We examined the surgical distal resection margin from a histopathological viewpoint. METHODS We enrolled 629 patients. The type of distal spread was evaluated, and the maximum length of distal spread was measured using a micrometer. RESULTS The frequencies of discontinuous spread type were 1.0%, 8.4%, 52.9%, and 81.5%, and the average lengths of distal spread were .5 ± 1.3 mm, 7 ± 1.8 mm, 2.7 ± 2.4 mm, and 10.0 ± 9.5 mm for well-differentiated adenocarcinomas, moderately differentiated adenocarcinomas, solid (por1)-type poorly differentiated adenocarcinomas, and nonsolid (por2)-type poorly differentiated adenocarcinomas, (moderately vs solid [por1] type: P = .004), respectively. CONCLUSIONS The surgical distal resection margin based on pathological diagnosis is longer somewhat than that based on macroscopic findings. Therefore, it is important to select surgical procedures with great care to ensure an adequate surgical distal resection margin.