Metastases from carcinoma of the colon and rectum detected in small lymph nodes by the clearing method

: A study of regional lymph node metastases was performed using the clearing method in 322 patients with carcinoma of the colon and rectum (140 with carcinoma of the colon and 182 with carcinoma of the rectum) who had undergone surgical resection. The mean number of nodes examined per patient was 76.4 and the metastatic rate (patients with metastases divided by the total of patients) was 61.4 percent, with a metastatic incidence (nodes with metastases divided by the total of examined nodes) of 6.4 percent for carcinoma of the colon using the clearing method. For carcinoma of the rectum, the mean number of nodes examined was 73.7 with a metastatic rate of 57.1 percent and a metastatic incidence of 7.1 percent. In contrast, node analysis by the conventional manual method resulted in a mean of 18.1 nodes being examined, with a metastatic rate and incidence of 42.1 and 12.8 percent, respectively, for carcinoma of the colon. Manual examination of lymph nodes in carcinoma of the rectum resulted in a mean of 21.2 nodes being examined, with a metastatic rate and incidence of 50.0 and 16.8 percent, respectively. Compared with the manual method, the clearing method provided a greater number of nodes, a higher metastatic rate and a lower metastatic incidence. These differences may be explained by the detection of metastatic regional nodes smaller than 4 millimeters in maximum diameter by the clearing method. By TNM classification there were more pN3 than pN2 lesions. The five year survival rate after curative resection was 78.5 percent for pN1 lesions, 45.7 percent for pN2 lesions and 45.4 percent for pN3 lesions for carcinoma of the colon and 72.7 percent for pN1 lesions, 75.0 percent for pN2 and 53.9 percent for pN3 lesions for carcinoma of the rectum. There was no significant survival difference between the patients with pN1, pN2 and pN3 carcinomas. The presence of regional nodes metastases should be examined in detail. Therapies and prognosis of carcinoma of the colon and rectum should be discussed based on accurate staging.