Pathology Research International interesting to know whether the mRNA expression patterns of GPC3, LYVE1, and survivin suﬀer from the same sort of intratumoral heterogeneity, which might complicate their use as molecular markers for HCC in needle biopsies. Although immunohistochemical staining for the GPC3/ HSP70/GS panel is currently recommended as the best ancil- lary technique to aid in the diagnosis of early HCC in diﬃcult needle biopsy specimens [44], the search continues for biomarkers that can increase the sensitivity of this panel and that are easily and reproducibly stainable in tissue sections. Most candidate markers have been discovered through gene expression studies, and beyond their practical diagnostic utility, investigation into their functions in human liver and in model systems has yielded important insights into the mechanisms of hepatic carcinogenesis. A recent example of gene expression proﬁling leading to this kind of basic insight is provided by Kaposi-Novak et al. in their study of dysplastic nodules and early HCC in cirrhotic liver explants [37]. In addition to identifying molecular signatures able to discrimi- nate between regenerative, dysplastic, and malignant nodules as well as conﬁrming the upregulation of HSP70, GPC3, and several other putative tumor markers in early HCC, these investigators performed a comparative functional analysis of DN and HCCs gene expression signatures. Their results show that the gene expression proﬁle of early HCCs diﬀers from that of DNs in a pattern strongly suggestive of MYC oncogene activation. Interestingly, no mutations in the MYC gene were detected by sequencing of HCC genomic DNA, and MYC itself was not found to be overexpressed. However, a protein called CSN5 (also known as Jab1) that had been previously shown to posttranscriptionally promote MYC activation in breast epithelium [45] was found to be overexpressed in early HCC in parallel with induction of the MYC-regulated gene expression signature. This suggests a mechanistic model of early hepatocarcinogenesis in which an increase in the expression of CSN5 within DN leads to aberrant MYC activation, and thereby drives the progression of these lesions to HCC. If this model proves true, it may have profound implications for the molecular classiﬁcation, diagnosis, and treatment of early HCC. 4.2. Hepatocellular Carcinoma Arising in Noncirrhotic Liver. The overall incidence of HCCs in patients without cirrhosis is diﬃcult to estimate and varies with geography and the prevalence of risk factors in the population [46, 47]. Most cases occur in association with chronic liver disease, sometimes in a background of hepatic ﬁbrosis that falls short of full-blown cirrhosis. Consequently, the risk factors for HCC development are the same in the absence of cirrhosis as in its presence; they include chronic HBV or HCV infection, chronic alcohol- or toxin-induced liver injury, and nonalcoholic steatohepatitis [46, 48]. Noncirrhotic patients with HCC are more likely than those with cirrhosis to have multiple risk factors. Although the molecular pathogenesis of hepatic malignancy is likely variable, with some genetic alterations more common in lesions that arise in association with particular risk factors than others, there is no strict correlation between the etiology of underlying chronic liver 7 disease and histologic or molecular subtype of HCCs (see below). Hepatocellular carcinomas that arise in the absence of chronic liver disease or known risk factors for malignancy are almost always a histologic variant known as ﬁbrolamellar HCC (FL-HCC). The great majority of these tumors occur in patients under the age of 35, and they display a characteristic histology, with nests of large, oncocytic, malignant hepato- cytes surrounded by thick bands of layered ﬁbrosis. Although the rarity of these tumors has hampered eﬀorts to elucidate their molecular pathogenesis, FL-HCCs have been found to contain unique molecular alterations that distinguish them from the more common forms of HCCs (reviewed in [49]). The diagnosis of FL-HCCs depends mostly on histology, with the application of immunohistochemical markers when needed [50], and the recognition of clinical characteristics typical of this distinct clinicopathologic entity. 4.3. Hepatocellular Carcinoma Heterogeneity. Hepatocellular carcinoma has long been known to display extraordinary genetic complexity and molecular heterogeneity. However, it is not clear which of the many genomic, genetic, and epigenetic alterations found in HCCs are the most critical in driving its molecular evolution and/or deﬁning its biological behavior. For this reason, there is currently no molecular subclassiﬁcation of HCCs that is widely accepted and rou- tinely implemented in clinical practice. Nonetheless, a host of molecular genetic markers have been found to correlate with clinical parameters, and in some instances, to have independent prognostic value in particular circumstances. Although in recent years, surveillance of those at high risk of hepatic malignancy has initiated a trend toward earlier diagnosis of liver cancer, a substantial majority of HCC patients still present with locally advanced or metastatic disease [51]. Even among those whose cancer is diagnosed at a stage early enough to allow them to undergo potentially curative therapy (such as resection, percutaneous ablation, or liver transplantation), the rate of tumor recurrence remains signiﬁcant. Overall long-term survival of patients with HCCs is poor, in part because most suﬀer from concomitant, underlying chronic liver disease. However, rates of recurrence and metastasis are not uniform, even within stage-matched patient groups, and there is evidence that from their beginnings, HCC tumors show individual variability in their degree of intrinsic biological aggressiveness [52]. In addition, the number of therapeutic options for HCCs is growing rapidly, due to advances in ﬁelds such as interventional radiology and transplantation as well as the emergence of a large armamentarium of molecularly targeted antineoplastic drugs [53, 54]. Thus, for HCC patients at all stages, there is a need for prognostic and predictive biomarkers that can aid in the subclassiﬁcation of these tumors and help to identify patients who are most likely to respond to each available treatment modality. 4.4. Chromosomal Abnormalities and Genetic Mutations in HCC. HCCs generally show a high level of chromosomal instability, and this is a phenotype that is acquired early