In tissues with no adult expression, GPC3 may act as an oncofetal protein, and tumors derived from these tissues have increased levels of GPC3 mRNA (hepatocellular carcinoma, hepatoblastoma, Wilms tumor, neuroblastoma, and rhabdomyosarcoma), with protein studies limited to the first three [7,10-13]. Here, GPC3 is linked to Wilms tumor.