Introduction: Some cases of colon cancer with positive lymph node metastasis, given equal lymph node dissection, show recurrence, while others do not. We therefore suspected differences in biological malignancy due to different occupancy of the cancer cells in cases with positive lymph node metastasis, and investigated the relationship between the occupancy and postoperative lymph node recurrence.
Methods: Of the cases of colon cancer without infiltration to the serosa (adventitia) that were resected between 1986 and 1995, we investigated 150 cases that were positive for lymph node metastasis. Of these, 77 cases that showed a less than 50% rate of tumor occupancy in the most distant lymph nodes positive for metastasis were classified as mild type, and the remaining 73 cases with a 50% or higher rate of occupancy as massive type. The clinicopathological factors, number of metastatic lymph nodes, metastatic site, greatest diameter, postoperative lymph node recurrence, and outcomes were investigated.
Results: Differences in clinicopathological factors were seen only in the tissue form of major tumors, with the massive type showing a significantly greater number of poorly differentiated adenocarcinoma and mucinous carcinoma than the mild type (p<0.01). The number of metastatic lymph nodes was significantly greater in the massive type (3.4) than in the mild type (2.0) (p<0.01). The greater lymph node diameter was significantly greater in the massive type (9.2) than in the mild type (5.7) (p<0.01). Postoperative lymph node recurrence was significantly more frequent in the massive type (17 cases, 23.3%) than in the mild type (2 cases, 2.6%) (p<0.05). The accumulated 5-year non-recurrence rate was significantly lower in the massive type (97.3%) than in the mild type (73.4%) (p<0.01).
Conclusion: These results suggest that the mild/massive classification reflects biological malignancy and may become a predictive factor for lymph node recurrence. Cases in which the postoperative histopathological findings show that the most distant lymph nodes positive for metastasis are of the massive type must be considered high risk for lymph node recurrence and require careful follow-up.