Impact of lymph node micrometastasis in patients with pancreatic head cancer

The purpose of this study was to investigate the clinical significance of nodal micrometastasis in patients who underwent a curative operation for pancreatic cancer.

Fifty-eight patients underwent a macroscopically curative resection with extended lymph node dissection for pancreatic cancer. The total number of resected lymph nodes was 1,058, and 944 histologically negative lymph nodes were subjected to immunohistochemical staining to detect occult micrometastases.

Nodal micrometastases were detected immunohistochemically in 147 out of 944 resected histologically negative lymph nodes (15.6%). Forty-four of all 58 patients (75.9%) and 13 of the 23 histologically node-negative patients (56.5%) had nodal micrometastases. Nodal micrometastases existed in the N1 lymph node area most frequently, followed by the N2 and N3 lymph node areas. The distribution was similar to that of histologically metastatic lymph nodes. Ten out of 16 patients (62.5%) with histological N1, and 5 out of 16 patients (31.3%) with histological N2 had nodal micrometastases beyond the histological lymph node status. Three and 5-year survival rates of pN0 patients without lymph node nodal micrometastases were both 60.0%, while those with nodal micrometastases were 19.2% and 0%, respectively. There was statistically significant difference between the both groups (P = 0.041).

Nodal micrometastasis in pancreatic cancer existed in wider and more distant areas than histological lymph node status, and it was an unfavorable predictive factor, even in N0 patients.