Detection and prediction of micrometastasis in the lymph nodes of patientswith pN0 gastric cancer

Background: The clinicopathologic significance of micrometastasis (MM) and tumor cell microinvolvement (TCM) in regional lymph nodes as identified by immunohistochemical staining for cytokeratin expression was evaluated in pa tients with node-negative gastric cancer. Methods: MM was defined as tumor cells with stromal reaction, and TCM was d efined as individual tumor cells without stromal reaction. We investigated 1761 lymph nodes obtained from 67 gastric cancer patients whose diagnosis s howed no lymph node metastasis by routine histological examination. The dep th of tumor invasion was T1 (submucosa) in 33 patients and T2 (muscularis p ropria and subserosa) in 34 patients. The lymph nodes were examined immunoh istochemically for the presence of tumor cells using anti-cytokeratin AE1/A E3 monoclonal antibody. Both the biopsy tumor specimens obtained prior to s urgery and the resected primary tumors were immunostained with E-cadherin ( E-cad) monoclonal antibody. Results: Thirty (1.5%) of the 1761 lymph nodes showed MM and/or TCM. MM wit h or without TCM was found in 10 patients, and TCM alone was found in 4 pat ients: 6 (18.2%) of the 33 patients with T1 tumor and 8 (23.5%) of the 34 p atients with T2 turner had occult lymph node metastasis. The 5-year surviva l rate was worse among those with MM with or without TCM, than among those without MM. Nearly all of the patients with MM and/or TCM had reduced or ne gative E-cad expression in the primary tumor. Conclusions: We demonstrated that the incidence of MM and/or TCM in the lym ph nodes of patients with gastric cancer is quite high, and that such metas tasis is associated with the prognosis of patients with pN0. Examination of E-cad expression in biopsy tumor specimens may be useful for predicting MM and/or TCM.