Immunohistochemistry and molecular detection of nodal micrometastases in pancreatic cancer

Purpose. Assays based on polymerase chain reaction (PCR) demonstrate mutated Kiras in the regional nodes of a majority of patients with node-negative stage I or II (T1-3, N-o, M-o) pancreatic adenocarcinoma. The hypothesis that the presence of mutated Kiras equates with micrometastases has not been validated by detailed histologic examination nor has an impact on survival been demonstrated. Methods. We examined the paraffin blocks of the primary tumor and regional lymph nodes from all 30 patients from 1984 to 1998 with resected pN(o) stage I or II pancreatic adenocarcinoma. DNA was analyzed for mutations in codon 12 of the Kiras oncogene by PCR and restriction digest with BstN1 (RFLP). All nodes were examined by histology of 4 hematoxylin and eosin-stained step sections and immunohistochemistry (HPE/IHC) with AE3/AE1 epithelial cell marker antibody. Results. Examination of the regional lymph nodes of the 30 patients demonstrated nodal metastases in 9 (30%) by step-section histology alone, 14 (46.7%) by HPE/IHC, 19 (63.3%) by PCR/RFLP, and 25 (83.3%) by a combination of PCR/RFLP and HPE/IHC. Seven cases were HPE/IHC positive yet PCR/RFLP negative while 10 cases were PCR/RFLP positive and HPE/IHC negative. Median survival (months) did not differ if nodes were negative or positive by HPE/IHC (20.5 vs 17.5) or PCR/RFLP (20.0 vs 19.0) or a combination of these techniques (25 vs 18.5). Conclusions. A great majority (83.3%) of patients with pathologic stage I or II: pancreatic cancer had metastases in their regional nodes. Step sectioning with immunohistochemistry and PCR/RFLP are complementary tests in detection of metastatic cancer cells. Nodal micrometastases did not adversely influence survival. (C) 2000 Academic Press.