Influence of micrometastasis on N stage in gastric cancer and clinical application.

In order to evaluate the real extent of lymph node metastasis (LNM) in gastric cancer, an immunohistochemical (IHC) analysis was performed. We examined 11173 lymph nodes removed from 355 patients with all stages of gastric carcinoma. Tissue preparations were stained with cytokeratin 18, monoclonal antibody against cytokeratin. Micrometastases were found in 2.5% of the lymph nodes and in 31.3% of patients. The incidence of the patients with LNM increased to 9.1% in T(1m) (n = 99), 31.6% in T(1sm) (n = 95, 23.1% in sm1, 34.8% in sm2), 66.7% in T2 (n = 108, 48.8% in mp, 76.5% in ss), 88.1% in T3 (n = 42), and 90.9% in T4 (n = 11) lesions. Upstage was identified in 8.5% of patients: 6.7% in T1 (4.0% in m, 7.7% in sm1, 10.1% in sm2), 14.8% in T2 (20% in mp, 11.8% in ss), 2.4% in T3, and 0% in T4. Factors related to LNM were: tumor size and lymphatic invasion in mucosal lesions; only lymphatic invasion in submucosal lesions; size and depth of tumor, and lymphatic invasion in T2 lesions. In conclusion, the incidence of micrometastasis in regional lymph nodes was higher than we imagined in T1 lesions, more than D1 lymphadenectomy for sm1 and selected cases of mucosal cancer, and D2 lymphadenectomy for sm2 are necessary.