CD146 is a cell surface glycoprotein, originally identified as a melanoma antigen, whose expression is associated with tumor progression and the development of metastatic potential. Overexpression of CD146 in breast carcinoma cells results in a more cohesive cell growth and in the formation of smaller tumors in nude mice. During implantation and placentation, CD146 is expressed by the intermediate trophoblast in the placental site and binds to its putative receptor in uterine smooth muscle cells thus limiting trophoblastic invasion in the myometrium.