This document summarizes a study that used quantitative image analysis of HER2 expression in esophagogastric adenocarcinoma tissue samples to identify prognostic factors. Automated image analysis was performed using the Definiens platform to extract over 50 image features from segmented cells and subcellular compartments. Multivariate regression analysis was able to predict disease-free and overall survival times from these quantitative image features, which were then shown to have prognostic value when analyzed with Kaplan-Meier survival curves. This demonstrated that automated quantitative image analysis can provide statistically significant prognostic factors not accessible to visual analysis alone.