PTK2 and breast cancer: ECM stiffness critically modulates breastcancer biology, driving cell proliferation, stemness, metastasis,and invasion through key signaling pathwayssuch as YAP/TAZ, Wnt/β-catenin,FAK, TWIST1, PI3K/AKT/mTORC1, and ROCK. Consequently, alterations in matrix stiffnesscan profoundly influence these signaling cascades, thereby affectingthe behavior of breast cancer cells, the functions of stromal cells,and responses to therapeutic interventions.