Pancreatic ductal adenocarcinoma continues to be one of the most difficult diseases to manage with one of the highest cancer mortality rates. This is due to several factors including nonspecific symptomatology and subsequent diagnosis at an advanced stage, aggressive metastatic behavior that is incompletely understood, and limited response to current therapeutic regimens. As in other cancers, there is great interest in studying the role of the tumor microenvironment in pancreatic ductal adenocarcinoma and whether components of this environment could serve as research and therapeutic targets. In particular, attention has turned toward the desmoplastic collagen-rich pancreatic ductal adenocarcinoma stroma for both biological and clinical insight. In this study, we used quantitative second harmonic generation microscopy to investigate stromal collagen organization and structure in human pancreatic ductal adenocarcinoma pathology tissues compared with non-neoplastic tissues. Collagen topology was characterized in whole-tissue microarray cores and at specific pathology-annotated epithelial-stroma interfaces representing 241 and 117 patients, respectively. We quantitatively demonstrate that a unique collagen topology exists in the periductal pancreatic ductal adenocarcinoma stroma. Specifically, collagen around malignant ducts shows increased alignment, length, and width compared with normal ducts and benign ducts in a chronic pancreatitis background. These findings indicate that second harmonic generation imaging can provide quantitative information about fibrosis that complements traditional histopathologic insights and can serve as a rich field for investigation into pathogenic and clinical implications of reorganized collagen as a pancreatic ductal adenocarcinoma disease marker. Pancreatic ductal adenocarcinoma is one of the most devastating human malignancies. It is currently the fourth leading cause of cancer death and projects to become the second leading cause by 2030. 1 The 5-year relative survival rate has remained in the single digits for decades. Pancreatic ductal adenocarcinoma is notoriously difficult to detect before an advanced, inoperable stage is reached due to nonspecific symptomatology and the retroperitoneal location of the pancreas, which makes palpation or routine biopsy of suspicious masses difficult. Recent advances in the sensitivity and specificity of preoperative imaging modalities such as computer tomography, magnetic resonance imaging, positron emission tomography, endoscopic ultrasonography, and endoscopic retrograde cholangiopancreatography have played an important role in enhancing pancreatic ductal adenocarcinoma diagnosis, detailing the relationship of lesions to nearby anatomical structures, and determining the course of management. 2 Despite these advances, only 10-15% of patients are diagnosed at a localized disease stage when surgical resection is possible as a potential curative therapy. However, postsurgical recurrence rates are high with 5-year survival rate of