Glypican-3 is a memer of glypican family of heparan sulfate proteoglycans that are anchored to the cell-surface via a covalent linkage to glycosylphosphatidylinositol. Glypicans can modify cell signaling pathways and contribute to cellular proliferation and tissue growth. GPC3 is a useful tumor marker for the diagnosis of hepatocellular carcinoma, hepatoblastoma, melanoma, testicular germ cell tumors, and Wilms tumor.