Only a minority of patients who undergo surgical resection for pancreatic ductal adenocarcinoma are cured. Since patient outcome is not reliably predicted using pathological factors (tumor stage, differentiation, and resection margin status) alone, markers of tumor behavior are needed. One candidate predictor of pancreatic cancer outcome is E-cadherin status. CDH1 is a tumor suppressor gene encoding an important cell adhesion molecule (E-cadherin). The aim of this study was to determine if, among patients undergoing pancreaticoduodenectomy for pancreatic adenocarcinoma, loss of E-cadherin expression was an independent predictor of poor outcome. We examined patterns of loss of E-cadherin by immunohistochemistry in tissue microarrays of 329 surgically resected pancreatic ductal adenocarcinomas. E-cadherin expression was then correlated with outcome. Kaplan-Meier analysis and Cox proportional hazards regression modeling were used to assess the mortality risk. One hundred forty-one pancreatic adenocarcinomas (43%) had partial or complete loss of E-cadherin expression within the analyzed tissue cores. In most instances (134 cases, 41%), this loss was partial. Patients whose pancreatic adenocarcinomas had either complete loss (n=7; median survival, 5.5 months) or partial loss (n=134; 12.7 months) of E-cadherin expression had significantly worse median survival than those with uniformly intact E-cadherin expression (n=188; 18.5 months) by univariate (P=0.002) and multivariate (P=0.006) analyses. In subgroup analysis, patients with poorly differentiated cancers had a worse prognosis if their cancers had partial loss of E-cadherin expression (P=0.02). Among patients undergoing pancreaticoduodenectomy for pancreatic ductal adenocarcinoma, partial loss of tumoral E-cadherin expression is an independent predictor of poor outcome.