Pathology Research International that approximately 10% of adenomas belong to this β-HCA subtype. Beta-catenin activation is most easily assessed through immunostaining for glutamine synthetase, which is diﬀusely overexpressed in these lesions. Alternatively, immunohistochemical staining for β-catenin itself may be used to distinguish between tumors without mutation, in which β-catenin has a membranous localization, and those with mutation, in which an aberrant, activated form of β- catenin accumulates within nuclei. In both I-HCA and β- HCA, β-catenin mutation has been associated with a high risk of malignancy. These tumors are common in men, and they often show features, such as pseudoacini and hepatocellular dysplasia, that are frequent in HCC. In fact, because β-HCA may be histologically indistinguishable from well-diﬀerentiated HCC [28], their existence as a biologically distinct entity has been called into question. A group in the United States has recently reported their failure to ﬁnd any examples of β-HCA in a collection of 41 adenomas subjected to molecular analysis [30]. We feel that in well-diﬀerentiated hepatocellular tumors, the presence of β-catenin mutation in association with morphologic features suspicious for malignancy should warrant a pathologic diagnosis of either outright or suspected hepatocellular carcinoma, rather than HCA. This is an area in need of further research to determine the molecular diﬀerences, if any exist, between β-HCA and HCC. Such ﬁndings would help to elucidate the pathogenesis of HCC and might serve as the basis for a diagnostic test of malignancy in histologically equivocal cases. The fourth and ﬁnal category of HCA are those that are noninﬂammatory (negative for acute phase markers) and do not harbor mutations in HNF1, β-catenin, or gp130. This is the smallest group of HCA, accounting for only about 5% of the total. Lesions that cannot be fully evaluated due to extensive necrosis and/or hemorrhage are also classiﬁed in this group. Whether these noninﬂammatory, nonmutant tumors represent a truly distinct subtype of HCA, or whether they are biologically related to one or more of the other three subtypes, is an open question that awaits further inves- tigation. 4. Hepatocellular Carcinoma (HCC) HCC almost always arises in the context of chronic liver disease, usually in patients with cirrhosis. Cirrhosis of any etiology constitutes the predominant risk factor for HCC. Worldwide, infection with hepatitis B virus (HBV) accounts for the majority of cases, whereas in the United States, chronic hepatitis C is the most common predisposing factor. HCC is often diagnosed late in the course of disease, but in developed countries, surveillance programs that use im- proved radiologic techniques for monitoring liver lesions in patients with cirrhosis are leading to increased rates of early HCC detection. 4.1. Dysplastic Nodules and Early Hepatocellular Carcinoma in Cirrhosis. It is now well accepted that in cirrhotic livers, the vast majority of HCC arise from benign precursor lesions called dysplastic nodules (DN) [31]. Although fully 5 Figure 3: Immunohistochemical staining for serum amyloid A (SAA) in an inﬂammatory HCA shows strong, diﬀuse positivity in the tumor (right) but virtually no staining in adjacent normal liver (left). developed HCCs typically show histologic features that are easily recognizable to pathologists, the morphologic distinction between advanced DN and early HCCs is often more subtle and can be very diﬃcult to identify, especially in needle biopsies [32]. As the molecular genetic events that drive the early steps of hepatic carcinogenesis are more fully elucidated, it is anticipated that molecular markers will be found that can help pathologists in making these clinically important distinctions. Indeed, in recent years, molecular analyses of the dysplasia-to-carcinoma pathway in cirrhosis have begun to yield valuable information for the recognition and classiﬁcation of early hepatic neoplasia. Several groups have used gene expression proﬁling to identify “molecular signatures” that can accurately distin- guish between DN and early HCC [33–37]. Perhaps the most promising of these studies is that of Llovet et al., which analyzed the expression patterns of 55 hepato carcinogenesis- related genes in dysplastic nodules and early HCCs of hepatitis C-infected patients. These authors identiﬁed a panel of only three genes (GPC3, LYVE1 and survivin) whose mRNA expression levels, as assessed by quantitative reverse transcription-PCR (qRT-PCR), were shown to cor- rectly predict malignancy in 19 out of 20 early HCCs and nonmalignancy in 16 out of 17 DNs. As a test for HCC in this sample set, the sensitivity of this 3-gene expression panel was 95% and its speciﬁcity was 94%. Two of the genes in the panel, GPC3 (which encodes glypican-3) and survivin, are expressed by hepatocytes and are upregulated in HCCs, as compared to DN. The third gene, LYVE1, is expressed by endothelial cells and is downregulated in malignancy. All three genes had been previously implicated in hepatic carcinogenesis, and their diﬀerential expression levels in DNs and HCCs is most likely independent of the underlying cause of cirrhosis. The advantage of using qRT-PCR to identify this sort of molecular signature is that the method is highly quan- titative, much more so than conventional immunohisto- chemistry, and, therefore, more objective. However, a disad- vantage is that it must be performed on pure lesional tissue,