Minimum number of lymph nodes that should be examined for the International Union Against Cancer/American Joint Committee on Cancer TNM classification of gastric carcinoma

The classification of lymph node metastasis based on the number of positive nodes has been adopted in the International Union Against Cancer/American Joint Committee on Cancer (UICC/AJCC) TNM classification of gastric carcinoma. However, the N classification (for condition of the regional lymph nodes) would be underestimated when the number of examined nodes were too small. To determine the minimum number of lymph nodes to examine for a correct classification, we analyzed 926 patients undergoing curative resection for gastric carcinoma. The number of metastatic lymph nodes correlated significantly with the number of examined lymph nodes. The pN0 patients with 10 to 14 examined nodes showed a significantly higher survival rate than did those with 5 to 9 examined nodes, and they had as good a prognosis as those with 15 or more examined nodes. In the pN1 and pN2 categories, patients with 29 or fewer examined nodes tended toward lower survival rates than did patients with 30 or more examined nodes. Among the patients who were classified as stage IA, the survival rate for those with 5 to 9 examined nodes was significantly lower than that for patients with 30 or more examined nodes. Among the patients classified as stage III, those with 10 to 19 examined nodes and those with 20 to 29 examined nodes had lower survival rates than did patients with 30 or more examined nodes. In conclusion, the minimum number of lymph nodes examined for a correct pN0 classification can be reduced from 15 to 10. For pN1-3 classifications, 20 or more nodes should be examined, and examining 30 or more lymph nodes may be desirable.