BACKGROUND AND OBJECTIVES: The clinical significance of lymph node micrometastasis (MM) for pN0 early gastric cancer is not well documented. The aim of this study is to clarify the risk factors of lymph node MM and the prognostic significance of the type of lymph node MM in patients with pN0 early gastric cancer. METHODS: We investigated the lymph node MM with using an anticytokeratin immunohistochemical stain in 160 patients with pN0 early gastric cancer who underwent curative resection between 2000 and 2005. RESULTS: We identified lymph node MM in 34 of 160 patients (21.3%), and in 84 of 1,656 lymph nodes (5.1%). MM occurred as single-cell type in 10 patients and as cell cluster type in 24 patients. MM was significantly associated with tumor size (P = 0.041) and lymphatic invasion (P = 0.008). The statistically significant prognostic factors affecting 5-year survival rates were depth of tumor invasion (P = 0.020), tumor size (P = 0.035), lymphatic invasion (P = 0.018), MM (P < 0.001), and type of MM (P < 0.001). Cox regression survival analysis revealed that the presence of MM, and particularly the cluster-type MM (P < 0.001), were independent prognostic factors in pN0 early gastric cancer patients. CONCLUSIONS: The incidence of lymph node MM in patients with node negative early gastric cancer was 21.3%, and cancer cell cluster type of MM proved a primary independent prognostic factor for pN0 early gastric cancer patients.
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