A Clinico-Pathologic Study of Clear-Cell Hepatocellular Carcinoma

The Liver and Glycogen: In Sickness and in Health

The liver is a major store of glycogen and is essential in maintaining systemic glucose homeostasis. In healthy individuals, glycogen synthesis and breakdown in the liver are tightly regulated. Abnormal glycogen metabolism results in prominent pathological changes in the liver, often manifesting as hepatic glycogenosis or glycogen inclusions. This can occur in genetic glycogen storage disease or acquired conditions with insulin dysregulation such as diabetes mellitus and non-alcoholic fatty liver disease or medication effects. Some primary hepatic tumors such as clear cell hepatocellular carcinoma also demonstrate excessive glycogen accumulation. This review provides an overview of the pathological manifestations and molecular mechanisms of liver diseases associated with abnormal glycogen accumulation.

Clear cell hepatocellular carcinoma: origin, metabolic traits and fate of glycogenotic clear and ground glass cells

Clear cell hepatocellular carcinoma (CCHCC) has hitherto been considered an uncommon, highly differentiated variant of hepatocellular carcinoma (HCC) with a relatively favorable prognosis. CCHCC is composed of mixtures of clear and/or acidophilic ground glass hepatocytes with excessive glycogen and/or fat and shares histology, clinical features and etiology with common HCCs. Studies in animal models of chemical, hormonal and viral hepatocarcinogenesis and observations in patients with chronic liver diseases prone to develop HCC have shown that the majority of HCCs are preceded by, or associated with, focal or diffuse excessive storage of glycogen (glycogenosis) which later may be replaced by fat (lipidosis/steatosis). In ground glass cells, the glycogenosis is accompanied by proliferation of the smooth endoplasmic reticulum, which is closely related to glycogen particles and frequently harbors the hepatitis B surface antigen (HBsAg). From the findings in animal models a sequence of changes has been established, commencing with preneoplastic glycogenotic liver lesions, often containing ground glass cells, and progressing to glycogen-poor neoplasms via various intermediate stages, including glycogenotic/lipidotic clear cell foci, clear cell hepatocellular adenomas (CCHCA) rich in glycogen and/or fat, and CCHCC. A similar process seems to take place in humans, with clear cells frequently persisting in CCHCC and steatohepatitic HCC, which presumably represent intermediate stages in the development rather than particular variants of HCC. During the progression of the preneoplastic lesions, the clear and ground glass cells transform into cells characteristic of common HCC. The sequential cellular changes are associated with metabolic aberrations, which start with an activation of the insulin signaling cascade resulting in pre-neoplastic hepatic glycogenosis. The molecular and metabolic changes underlying the glycogenosis/lipidosis are apparently responsible for the dramatic metabolic shift from gluconeogenesis to the pentose phosphate pathway and Warburg-type glycolysis, which provide precursors and energy for an ever increasing cell proliferation during progression.

Clinicopathological indices to predict hepatocellular carcinoma molecular classification

BACKGROUND & AIMS

Hepatocellular carcinoma (HCC) is the second most lethal cancer caused by lack of effective therapies. Although promising, HCC molecular classification, which enriches potential responders to specific therapies, has not yet been assessed in clinical trials of anti-HCC drugs. We aimed to overcome these challenges by developing clinicopathological surrogate indices of HCC molecular classification.

METHODS

Hepatocellular carcinoma classification defined in our previous transcriptome meta-analysis (S1, S2 and S3 subclasses) was implemented in an FDA-approved diagnostic platform (Elements assay, NanoString). Ninety-six HCC tumours (training set) were assayed to develop molecular subclass-predictive indices based on clinicopathological features, which were independently validated in 99 HCC tumours (validation set). Molecular deregulations associated with the histopathological features were determined by pathway analysis. Sample sizes for HCC clinical trials enriched with specific molecular subclasses were determined.

RESULTS

Hepatocellular carcinoma subclass-predictive indices were steatohepatitic (SH)-HCC variant and immune cell infiltrate for S1 subclass, macrotrabecular/compact pattern, lack of pseudoglandular pattern, and high serum alpha-foetoprotein (>400 ng/ml) for S2 subclass, and microtrabecular pattern, lack of SH-HCC and clear cell variants, and lower histological grade for S3 subclass. Macrotrabecular/compact pattern, a predictor of S2 subclass, was associated with the activation of therapeutically targetable oncogene YAP and stemness markers EPCAM/KRT19. BMP4 was associated with pseudoglandular pattern. Subclass-predictive indices-based patient enrichment reduced clinical trial sample sizes from 121, 184 and 53 to 30, 43 and 22 for S1, S2 and S3 subclass-targeting therapies respectively.

CONCLUSIONS

Hepatocellular carcinoma molecular subclasses can be enriched by clinicopathological indices tightly associated with deregulation of therapeutically targetable molecular pathways.

Molecular classification of hepatocellular carcinoma: potential therapeutic implications

Genomic profiling of hepatocellular carcinoma (HCC) tumors has elucidated recurrent molecular aberrations common or specific to disease etiology, patient race or geographic regions, allowing the classification of HCC tumors into subclasses sharing similar molecular and clinical characteristics. Previously reported transcriptome-based molecular subclasses have highlighted several common themes. Aggressive tumors are characterized by TP53 inactivation mutations and activation of pro-oncogenic signaling pathways, and further subclassified according to expression of stemness markers. The stemness marker-negative aggressive tumors display preferential TGF-β activation. Another group of less aggressive tumors contains a subclass characterized by CTNNB1 mutations accompanied with overexpression of liver-specific WNT targets such as GLUL. Molecular therapies selectively targeting features of the HCC subclasses have suggested their utility in enriching potential responders in clinical trials and guiding therapeutic decision-making for HCC patients.

Clear-cell carcinoma: an ultrastructural study of 57 tumors from various sites

Clear-cell carcinoma is a convenient and frequently used descriptive term for a malignant epithelial neoplasm that is entirely or largely composed of cells with optically clear cytoplasm in hematoxylin-eosin-stained sections. Transmission electron microscopy was performed on 57 tumors from various sites to investigate the fine structural basis for the clarity of the cytoplasm. The clear appearance resulted from the presence of one or several of the following features, as the sole or predominant cause or in combination: glycogen, lipid droplets, mucin vacuoles or diffuse mucosubstances, dilated cisternae, swollen or unusually large mitochondria, large solitary membrane-limited vacuoles or numerous smaller vacuoles, intracytoplasmic lumens, expanded intercellular spaces, cytoplasmic pseudoinclusions, and a paucity of organelles. Degenerative changes contributed to the clear appearance by inducing swelling of mitochondria and creating lucent cytosol. The factors responsible for the clear cytoplasm were not always consistent with regard to tumor type or site of origin, but glycogen was the commonest reason among the 57 tumors studied and the principal cause in tumors of the female genital tract, skin, and salivary glands, while renal cell carcinomas tended to possess an admixture of glycogen and lipid droplets. Because of the heterogeneity of the subcellular changes that can produce optically clear cytoplasm, electron microscopy has a limited role in determining the primary site of a metastatic clear-cell carcinoma.

Clinicopathologic study on clear cell hepatocellular carcinoma

In order to study the clinicopathologic characteristics of the clear cell variant of hepatocellular carcinoma (HCC), 215 consecutive cases measuring less than 5 cm in diameter were reviewed. The cases were divided into clear cell HCC (20 cases); focal clear cell HCC (77 cases); and non-clear cell HCC (118 cases). Clinical and pathological findings were compared among these groups. Clear cell HCC was moderately differentiated in 80% of cases and the incidence was not related to tumor size. The male to female ratio was 2.3:1, lower than the 6.9:1 of non-clear cell HCC. The association rate with liver cirrhosis was 90%, higher than the 59.3% of non-clear cell HCC. Three- and five-year survival rates, and no recurrence time were 54.5%, 33.3%, and 564 days, respectively, lower than the findings of 74.3%, 46.1%, and 770 days for non-clear cell HCC. But there is no significant difference in prognosis between both groups. Ultrastructurally, clear cells showed abundant glycogen storage and a variable degree of fat vacuoles, with a marked reduction of the number and size of organelles in the 8 cases examined. Non-clear cells of focal clear cell and non-clear cell HCC showed a moderate degree of glycogen storage in 85.7% and 28.6% of the seven cases examined from each group, with significant difference. It was concluded that clear cell HCC occurs mostly in the moderately differentiated form and is characterized by high female prevalence, high rate of association with liver cirrhosis, and has no significant difference in prognosis compared with non-clear cell HCC.

Hepatic neoformations

The aim of the paper is an accurate histologic description and illustration of those liver lesions that are usually summarized under the heading of "hepatic tumors and related subjects". For in some cases it may be unclear or at least controversial, whether the individual lesion is indeed an autonomous neoplasia or a malformation, regeneration or hyperplasia, the indifferent master term of neoformation is introduced, based on the fact that all of them are characterized by a cellular multiplication. According to common definitory practice the survey distinguishes between mesenchymal (angiomatous and non angiomatous) and epithelial neoformations. Among the latter hepatocellular and cholangiocellular types are distinguished, the criterium for differentiation being a phenomenological one, which is by no means identical with a histogenetical statement. The definition of subgroups mostly adheres to current nomenclatory usage; only occasionally--in the group of endothelial tumors--a novel term is employed, in view of brevity and coordination with the overall system of neoformations.