The human CD146 gene maps to chromosome 11q23 and encodes a trans-membrane glycoprotein, also designated MCAM, MUC 18, that belongs to the immunoglobulin superfamily and functions as a Ca2+-independent cell adhesion molecule. CD146 expression is restricted to advanced primary and metastatic melanomas and to cell lines of the neuroectodermal lineage, but not normal melanocytes. CD146 is found on 80% of advanced primary human melanomas and correlates well with development of metastatic disease.