KRT19 and neoplasm: The PDOs generated from eight patients with PDA (Table S3, Supporting Information) were confirmed to have similar cell components with their original tumors using immunofluorescence analysis (Figure 8B), in which epithelial cell marker (CK19+), cancer‐associated fibroblast (αSMA+) and endothelial cells (CD31+) were characterized as the essential components of tumor tissue.