Lymph node metastases detected in the mesorectum distal to carcinoma of the rectum by the clearing method: justification of total mesorectal excision.

Abstract

Total mesorectal excision effectively reduces the local recurrence rate of carcinoma of the rectum. This study was undertaken to clarify the rationale for total mesorectal excision. We retrospectively reviewed the records of 198 patients who underwent resection of a carcinoma of the rectum. The presence of nodal metastases in the mesorectum distal to the primary tumor was examined by the clearing method. The metastatic rate in the distal mesorectum was 20.2 percent. The metastatic rates according to the extent and site of the tumor were as follows: pT1, 0 percent; pT2, 0 percent; pT3, 21.9 percent; pT4, 50 percent; rectosigmoid, 10 percent; upper rectum, 26.3 percent; and lower rectum, 19.2 percent. The longest distal spread from the primary tumor to the metastatic node was 2 cm in carcinoma of the rectosigmoid, 4 cm in carcinoma of the upper rectum, and 3 cm in carcinoma of the lower rectum. Total mesorectal excision is required for patients with T3 and T4 tumors in the lower rectum, and excision of all mesorectal tissue down to at least 5 cm below the tumor is required for patients with T3 and T4 tumors in the upper rectum.