Abstract: The present invention concerns a method to determine the gene expression profile on a sample previously obtained from a patient diagnosed for a liver tumor, comprising assaying the expression of a set of genes in this sample and determining the gene expression profile (signature). In a particular embodiment, said method enables to determine the grade of liver tumor, such as hepatoblastoma (HB) or a hepatocellular carcinoma (HCC). The invention is also directed to kits comprising a plurality of pairs of primers or a plurality of probes specific for a set of genes, as well as to solid support or composition comprising a set of probes specific for a set of genes. These methods are useful to determine the grade of a liver tumor in sample obtained from a patient, to determine the risk of developing metastasis and/or to define the therapeutic regimen to apply to a patient.