Prognostic effect of lymph node micrometastasis in patients with histologically node-negative gastric cancer

Background There is no consensus as to the impact of lymph node micrometastasis on survival of patients with gastric cancer. The aim of this study was to clarify the prognostic significance of lymph node micrometastasis in patients with histologically node-negative gastric cancer Methods Lymph nodes (n=2039) from 64 patients with histologically node-negative gastric cancer (T2, T3) were evaluated for micrometastasis. Three serial 5-μm sections of the resected lymph nodes were prepared for immunohistochemical staining with the anti-cytokeratin antibody CAM 5.2. Results Micrometastasis was found in 73 of 2039 nodes (4%) and 20 of 64 patients (32%). The 5-year survival rate was significantly lower for patients with lymph node micrometastasis than for those without lymph node micrometastasis (66% vs. 95%,P<.01). The 5-year survival rate was significantly lower when there were four or more positive micrometastatic nodes (94% vs. 29%,P <.01) and when there were extragastric micrometastatic nodes (89% vs. 53%,P<.01). Conclusions Lymph node micrometastasis was associated with poor outcome in patients with histologically node-negative gastric cancer. The number and the level of lymph node micrometastases are useful prognostic markers for deciding treatment strategies for additional therapy and follow-up.