GPC3 and hepatocellular carcinoma: We chose to also use GPC3 in our panel to identify tumor cells because it is established to be one of the only proteins elevated in both HB35 and HCC.36 Finding a common marker is particularly challenging because these tumors are composed of cells of different lineages; HB is an embryonal tumor with both epithelial and mesenchymal areas1 while HCC is composed only of cells with an epithelial origin.44 Thus, other, more well-established cancer markers are not specific to both of these tumors.