Extracellular matrix protein 1 (ECM1) is involved in endochondral bone formation as a negative regulator of bone mineralization. ECM1 stimulates the proliferation of endothelial cells and promotes angiogenesis. ECM1 inhibits MMP9 proteolytic activity. Defects in ECM1 are the cause of lipoid proteinosis (LiP), also known as lipoid proteinosis of Urbach and Wiethe or hyalinosis cutis et mucosae. LiP is a rare autosomal recessive disorder characterized by generalized thickening of skin, mucosae and certain viscera. ECM1 is expressed in breast cancer tissues. Little or no expression is observed in normal breast tissues.