SPP1 and breast carcinoma: Specific ligand‐receptor interactions were observed between these epithelial subtypes and fibroblasts, with significant interactions between CD74‐APP receptors in SCGB3A1‐Epi and Fib‐11 in breast cancer and between SPP1‐CD44 receptors in KLK10‐Epi and Fib‐11 in PDAC.