Integrins are major extracellular matrix (ECM) receptors that can also serve for some cell-cell interactions. They have been identified as important regulators of mammary epithelial cell growth and differentiation. Their ability to promote cell anchorage, proliferation, survival, migration, and the induction of active ECM-degrading enzymes suggests that they play an essential role in normal mammary morphogenesis, but, on the other hand, reveals their potential to promote tumor progression.