Patterns of lymph node metastasis are different in colon and rectal carcinomas

To describe patterns of lymph node metastasis in invasive colon and rectal carcinomas.

Clinical data of 2340 patients with colorectal carcinoma (stage I to III) who received radical resection, was retrospectively reviewed. Of the 2340 patients, 1314 patients suffered from rectal carcinoma and 1026 from colon carcinoma. Patients with rectal cancer who received neoadjuvant chemoradiation therapy were excluded. Statistical analysis was performed using Mann-Whitney, χ(2) and Cochran's and Mantel-Haenszel tests (SPSS 15.0). A two-tailed P < 0.05 was considered statistically significant.

Lymph node retrieval in the rectal carcinoma group was significantly lower than that in the colon carcinoma group (P < 0.001), while positive lymph node retrieval in the rectal carcinoma group was significantly higher than that in the colon carcinoma group (P < 0.001). The proportion of lymph node positive (N+) cases was higher (patients with one or more positive lymph nodes) in the rectal carcinoma group (P = 0.004). The number of N+ cases was compared at different T stages (T1-T4) to eliminate background bias and the results were confirmed (P < 0.001). In addition, the lymph node ratio (the ratio of number of positive lymph nodes over the number of lymph nodes examined) of stage III cases in the rectal carcinoma group was significantly higher than that in the colon carcinoma group (P < 0.001).

Rectal carcinomas seem more prone to metastasize to the lymph nodes than colon carcinomas, which may be of potential clinical significance.