H epatocellular carcinomas (HCC) and hepatoblastomas of childhood (HPBL) are two types of liver cancer with high mortality and morbidity and international prevalence. There have been several recent studies of patterns of gene expression and molecular classification of HCC. [1][2][3][4] The studies demonstrated that HCC can be clustered in subgroups of gene expression patterns that have different prognostic and clinical behavior. Other recent studies also examined similarities between HCC precursor lesions (low and high grade liver nodules) and demonstrated significant similarities but also differences between HCC and precursor lesions. 5 In this study, we also focused on gene expression of HCC and HPBL, but from a different perspective than previous studies. We utilized a set of tissues from normal liver (NL), HCC, HPBL and tumor adjacent (AT) tissues and determined gene expression patterns not as a ratio of tumor vs. normal, but rather as absolute separate values for each unique tissue. This allowed standard but stringent statistical analysis not feasible when gene expression is only viewed as a fold change over normal tissues. Identification of gene expression patterns of liver tumors from this perspective allows identification of the main differences between the tumor subtypes and the adjacent nontumor (but often cirrhotic) liver; it also offers the potential of defining new therapeutic and diagnostic modalities. Our findings include some genes already shown to increase in HCC, thus validating our overall approach. Our results also revealed many other genes, not so far involved with biology of liver tumors. In addition, we carried a whole genome analysis of 27 HCC and determined chromosomal loci with genetic abnormalities common to most of the HCC. Materials and MethodsSee Supplemental information at the HEPATOLOGY

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