79 Evaluation of the 7th UICC TNM Staging System of Gastric Cancer In other words, it was recommended that lymph nodes be classified based on the anatomical location. On the other hand, the fifth edition recommends that the lymph nodes be classified based on the number of lymph nodes with a metastasis. Major revisions on the current seventh edition include the following: (1) Changes in the methods for classifying lymph nodes (2) Changes in the definition of TNM stage IV (3) Changes in the application of the disease staging to the eso- phago-gastric junction (4) The classification of positive cases to a peritoneal washing cytology to a distant metastasis. Given this background, this study analyzed the significance of these changes and examined the matters that need to be considered in the future classification of the disease stage. The Scope of the Classification of Lymph Nodes with Metastasis A revision was made for the definitions on the seventh edition when they were based on the number of lymph nodes observed on the fifth and the sixth edition. In other words, in the seventh edition, which unlike the previous classifications in that the number of lymph nodes with a metastasis of 1~6, 7~15 and ≥16 were classified as N1, N2 and N3, respectively, those in which the number of lymph nodes with a metastasis was 1~2, 3~6, 7~15 and ≥16 were classified as N1, N2, N3a and N3b, respectively. N3a and N3b were classified as the same stage. According to Ha et al.,(2) there was a significant difference in the survival rate between N3a and N3b. In particular, in the seventh edition, all cases with a metastasis in more than 7 lymph nodes were classified as N3. Compared to N1 or N2, there was a wider standard deviation in the number of lymph nodes with a metastasis (N1: 0.49, N2: 1.10 and N3: 13.77). This indicates that there is great variability in the number of lymph nodes with a metastasis in patients who belong to the N3 group. Based on the cut-off value of the number of lymph nodes with a metastasis of 30, N3 was subclassified into N3a (the number of lymph nodes with metastasis: 7~15), N3b (the number of lymph nodes with metastasis: 16~30) and N3c (the number of lymph nodes with metastasis: ≥31). This was followed by an analysis of the survival rate between the three subgroups in those patients with TanyN3M0. This showed that there was a significant difference in the survival rate between the three groups (P＜0.0001). In addition, following a comparison of the survival rate between the TanyN3cM0 group and stage IV based on the degree of the invasion to the gastric wall, there was a significant difference in the survival rate between T3N3cM0 and stage IV and that between T4aN3cM0 and stage IV (P=0.044 and P=0.007, respectively). On the other hand, there was no significant difference in the survival rate between T4bN3cM0 and stage IV. In other words, T4bN3cM0 was classified as stage IIIc in the seventh edition but it was found to be too poor to have a significant difference in the survival rate compared to stage IV. As described herein, there was no significant difference in the survival rate, even though there was a significant difference and the other disease stages were determined, even in cases for which the same disease stage was determined on the TNM staging system in the seventh edition (In press). According to Huang et al.,(3) few cases with early-stage gastric cancer had more than 6 lymph nodes with a metastasis. These authors reported that there were almost no cases corresponding to N2 (7~15) and N3 (＞15) based on the TNM staging on the fifth edition. They also noted that the difference in survival rate between N2 and N3 was significant after re-classifying N into N1 (1~3), N2 (4~6) and N3 (＞6), even though there was no significant difference in the survival rate between N2 and N3. This point of view was reflected appropriately in the seventh edition of TNM staging. If one should analyze these study results, he or she would be skeptical about whether there would be a difference in the methods for applying the TNM staging to progressive gastric cancer and early-stage gastric cancer. Some reports have shown that the classification of lymph nodes proposed on the seventh edition was better in predicting the prognosis compared to the sixth edition(4-6) but there are also dissenting reports.(2,7) A further subclassification of the lymph nodes would be useful for predicting the prognosis of each case. Other aspects are present that would cause many problems with clinical applications due to a very complicated staging system. In consideration of this, further studies will be needed to develop a staging system by harmonizing the two aspects that classifications should be made more specifically and then be uncomplicated. The Number of Lymph Nodes That Were Dissected The sixth edition of UICC TNM staging system declared that a pathological examination should be performed to make an accurate assessment of the degree of lymph node metastasis in more than 15 lymph nodes. According to the seventh edition, based on the statement “Any cases in whom no metastases are detected in all