Different patterns of lymphatic spread of sigmoid, rectosigmoid, and rectal cancers

Purpose: We tried to evaluate the clinicopathological characteristics of rectosigmoid cancer compared with those of sigmoid and rectal cancer. Methods: We collected data on patients who underwent curative resections for sigmoid (399; SC group), rectosigmoid (175; RS group), and upper rectal cancer (453; RA group) between June 1996 and December 2007. Results: The mean distance from the anal verge was 12.5 cm for rectosigmoid cancer, 13 cm for sigmoid cancer, and 9.8 cm for rectal cancer. The most common metastatic lymph nodes were pararectal nodes for the RS and RA groups and sigmoid mesenteric lymph nodes for the SC group. In a comparison of categories N2 and N1 for SC and RA groups, the increase of the metastasis rate was similar for all lymph nodes groups. However, for the RS group, the increase of metastasis to pararectal nodes was prominent in the N2 category. Overall recurrence and disease-free survival rate were not different among the groups. For stage III disease, the local recurrence rate was significantly higher in the RA group; the disease-free survival rate was higher in the SC group, and the RS group showed results similar to those of the RA group. Conclusion: Clinicopathological characteristics of rectosigmoid cancer were similar to those of sigmoid or rectal cancer. For lymphatic spreads, it was different from sigmoid or rectal cancer and more frequently metastasized to pararectal nodes. Oncologic results were slightly unfavorable to sigmoid colon, and showed data similar to those of rectal cancer. Therefore, rectosigmoid cancer was a "real" classification of colorectal cancer with unique lymphatic spread.