Ferrell, Linda D.

Abstract Objectives Cirrhosis-like hepatocellular carcinoma (CL-HCC) is a rare hepatocellular malignancy characterized by multiple tumor nodules that clinically, radiologically, macroscopically, and microscopically mimic cirrhosis. We aimed to elucidate the molecular biology of CL-HCC and determine tumor nodule clonality. Methods We performed RNA sequencing on formalin-fixed, paraffin-embedded tissue from confirmed CL-HCC cases (n = 6), along with corresponding nonneoplastic hepatic tissue (n = 4) when available. Transcriptomes from our previous work on steatohepatitic hepatocellular carcinoma and The Cancer Genome Atlas (TCGA) were used for comparison purposes. Results Histologically, CL-HCC displayed innumerable nodules and extensive vascular invasion. Intratumoral nodule comparison indicated that the multiple nodules were all clonally related, not independent primaries. The unique histomorphologic appearance corresponded with a distinct transcriptome compared with other HCCs, including fibrolamellar HCC (n = 6), steatohepatitic HCC (n = 8), and conventional HCC in TCGA (n = 424). Tumor-normal gene expression analysis revealed consistent overexpression of several genes involved in degradation of tissue matrix. No recurrent translocations or point mutations were identified. CL-HCC showed a gene expression profile indicative of zone 2 hepatocytes. Conclusions CL-HCC’s distinctive clinicopathologic features correspond to a unique gene expression profile, increased expression of invasive markers, features of zone 2 hepatocytes, and features suggestive of intratumoral nodule monoclonality.

Abstract The precise characterization of the lobular architecture of the liver has been subject of investigation since the earliest historical publications, but an accurate model to describe the hepatic lobular microanatomy is yet to be proposed. Our aim was to evaluate whether Voronoi diagrams can be used to describe the classic liver lobular architecture. We examined the histology of normal porcine and human livers and analyzed the geometric relationships of various microanatomic structures utilizing digital tools. The Voronoi diagram model described the organization of the hepatic classic lobules with overall accuracy nearly 90% based on known histologic landmarks. We have also designed a Voronoi-based algorithm of hepatic zonation, which also showed an overall zonal accuracy of nearly 90%. Therefore, we have presented evidence that Voronoi diagrams represent the basis of the two-dimensional organization of the normal liver and that this concept may have wide applicability in liver pathology and research.

Steatohepatitis-like change has not been described in focal nodular hyperplasia (FNH). Steatohepatitis-like change in FNH may show overlapping features with steatohepatitic variant of hepatocellular carcinoma (HCC). This problem can be compounded if seen in FNH with widened cell plates or hepatocyte rosettes, other features that can also be seen in HCC. This study examined steatotic FNHs for the frequency of steatohepatitis-like change, especially in the setting of FNH with rosettes and/or widened cell plates. Thirty-three resection specimens of steatotic FNH from 3 institutions were evaluated for degree of steatosis, background liver steatosis, ductular reaction, and lymphocytic infiltrate, as well as presence of thick fibrous bands, thick-walled vessels, ballooned hepatocytes, Mallory-Denk bodies, dilated sinusoids, hepatocyte rosettes, and thick hepatic plates. Steatosis was distributed along fibrous septa as well as diffusely throughout the FNH. Steatohepatitis-like changes were focally present in 54% (18 cases). Thick plates>3 cells were focally found in 14 cases (42%); rosettes were common (70%). All cases showed at least 2 of the histologic features highly suggestive for the diagnosis of FNH such as thick bands of fibrosis, thick-walled vessels and/or ductular reaction and the typical map-like pattern of glutamine synthetase immunostaining. More than half of fatty FNH examined for this study had features of at least focal steatohepatitis-like changes. This finding should not be confused with steatohepatitic variant of HCC. Common typical features of FNH including thick-walled vessels, ductular reaction and thick fibrous bands are helpful for discrimination of FNH from HCC.

Liver vasculature is crucial for adequate hepatic functions. Global deletion of Notch signaling in mice results in liver vascular pathologies. However, whether Notch in endothelium is essential for hepatic vascular structure and function remains unknown. To uncover the function of endothelial Notch in the liver, we deleted Rbpj, a transcription factor mediating all canonical Notch signaling, or Notch1 from the endothelium of postnatal mice. We investigated the hepatic vascular defects in these mutants. The liver was severely affected within 2 weeks of endothelial deletion of Rbpj from birth. Two‐week old mutant mice had enlarged vessels on the liver surface, abnormal vascular architecture, and dilated sinusoids. Vascular casting and fluorosphere passage experiments indicated the presence of porto‐systemic shunts. These mutant mice presented with severely necrotic liver parenchyma and significantly larger hypoxic areas, likely resulting from vascular shunts. We also found elevated levels of VEGF receptor 3 together with reduced levels of ephrin‐B2, suggesting a possible contribution of these factors to the generation of hepatic vascular abnormalities. Deletion of Rbpj from the adult endothelium also led to dilated sinusoids, vascular shunts, and necrosis, albeit milder than that observed in mice with deletion from birth. Similar to deletion of Rbpj, loss of endothelial Notch1 from birth led to similar hepatic vascular malformations within 2 weeks. Conclusions: Endothelial Notch signaling is essential for the development and maintenance of proper hepatic vascular architecture and function. These findings may elucidate the molecular pathogenesis of hepatic vascular malformation and the safety of therapeutics inhibiting Notch. (Hepatology 2016;64:1302‐1316)