or absence of lymph node metastases. Patients with gastric cancer with invasion within the MP (MP gastric cancer) in Japan account for about 10% of all gastric cancer patients undergoing a surgical resection [1,2]. MP gastric cancer is usually treated by a curative surgical resection, and the 5-year survival rate was reported as 72% to 82% [3,4]. Although most patients with MP gastric cancer are cured by an R0 resection, 16% to 22% of these patients have recurrences postoperatively [3,5].There are many reports that the subclassifi cation of gastric cancer with invasion within the submucosal layer (SM gastric cancer) is useful to predict lymph node metastasis [6,7]. It remains unclear, however, whether subdivision of tumor invasion into the MP is useful for predicting lymph node metastasis and prognosis [8,9]. In general, the MP is histologically divided into three layers; namely, the innermost oblique, the inner circular, and the outer longitudinal layers. Actually it is diffi cult to distinguish the innermost oblique and inner circular layers of the stomach under a microscope. However, it is easier to distinguish the inner circular and outer longitudinal layers. These results and facts suggest that the subdivision of MP gastric cancer into cancers in the inner circular and outer longitudinal layers might therefore make it possible to predict the prognosis of patients with MP gastric cancer. The present study evaluated the infl uence of the extent of tumor invasion into the MP.
Patients and methodsFrom 1983 to 2002, 798 consecutive patients underwent gastrectomy with lymph node resection for primary gastric cancer at Kumamoto University Hospital. Of these 798 patients, 72 (9.0%) patients had invasion within the MP. In 60 of these 72 patients, clinical data, including the surgical records, the histological fi ndings, Abstract Background. The muscularis propria of the stomach is histologically divided into three layers; namely, the innermost oblique, the inner circular, and the outer longitudinal layers. In patients with gastric cancer the depth of tumor invasion has been reported to correlate with lymph node metastasis and prognosis . However, it is unclear whether the depth of tumor invasion in the muscularis propria has an effect on lymph node metastasis and prognosis. Methods. Fifty-nine gastric cancer patients with muscularis propria invasion were analyzed retrospectively. These patients were divided into two groups, the inner group, with invasion up to the inner circular layer; and the outer group, with invasion beyond the inner circular layer. The relationships between tumor invasion and clinicopathological factors and survival were evaluated. Results. Of the 59 patients, 34 were classifi ed as the inner group, and 25 were classifi ed as the outer group. The inner group had a signifi cantly lower probability of lymph node metastasis (P = 0.0053) and a signifi cantly better overall cancer-specifi c survival (P = 0.017) than the outer group. Conclusion. Gastric cancers with muscularis propria invasion had het...