CD44 and neoplasm: As cluster of differentiation-44 (CD44) and epithelial-specific antigen (ESA) are PCSC cell surface markers, one study analysed PDAC surgical resection tissue (n = 93) and found that a ‘loose’ stroma with fewer fibroblasts was highest in CD44+/ESA− (63%) and CD44+/ESA+ (50%) tumours and that a dense, fibroblast-rich stroma was highest in CD44−/ESA− tumours.