Clinical Implications of Immunohistochemically Demonstrated Lymph Node Micrometastasis in Resectable Pancreatic Cancer

The purpose of this study was to determine the clinical significance of nodal micrometastasis detected by immunohistochemistry in patients that had undergone curative surgery for pancreatic cancer. Between 2005 and 2006, a total of 208 lymph nodes from 48 consecutive patients with pancreatic cancer that had undergone curative resection were immunostained with monoclonal antibody against pan-ck and CK-19. Micrometastasis was defined as metastasis missed by a routine H&E examination but detected during an immunohistochemical evaluation. Relations between immunohistochemical results and clinical and pathologic features and patient survival were examined. Nodal micrometastases were detected in 5 (29.4%) patients of 17 pN0 patients. Nodal micrometastasis was found to be related to tumor relapse (P = 0.043). Twelve patients without overt nodal metastasis and micrometastasis had better prognosis than 5 patients with only nodal micrometastasis (median survival; 35.9 vs 8.6 months, P < 0.001). The Cox proportional hazard model identified nodal micrometastasis as significant prognostic factors. Although the number of patients with micrometastasis was so small and further study would be needed, our study suggests that the lymph node micrometastasis could be the predictor of worse survival and might indicate aggressive tumor biology among patients undergoing curative resection for pancreas cancer.