A triple stain of reticulin, glypican-3, and glutamine synthetase: a useful aid in the diagnosis of liver lesions

Incidental findings during donor liver assessment: Single center experience

Intraoperative consultation of donor liver is an important part of transplant evaluation and determination of liver eligibility. In this study, we describe incidental pathologic findings discovered during the pretransplant evaluation of liver donors in our Institution from 1/2010 to 12/2022. During this 13-year period 369 intraoperative consultations from 262 liver donors were performed. Of those cases, incidental findings were identified in 22 cases (5.9 %) from 19 donors (7.3 %); two donors had more than one lesion. The median age of this subset of patients was 53 years (range: 18-70) and females predominated (63 %). Sixteen of the donors had abnormal findings in the liver: 6 bile duct hamartoma (BDH), 5 hyalinized nodule with Histoplasma capsulatum, 5 focal nodular hyperplasia (FNH), 2 bile duct adenomas (BDA), 1 biliary cyst and 1 hemangioma. One donor had both FNH and a BDH. One BDH and 1 BDA case was misdiagnosed as malignancy during the frozen section evaluation. Three donors had extrahepatic pathologies: a pancreatic tail schwannoma, a low-grade appendiceal mucinous neoplasm, and a lymph node with metastatic endometrial endometrioid adenocarcinoma. Of the 19 livers, the final organ disposition was available for 9: 6 were transplanted (67 %) and 3 were discarded (33 %). Two of the 3 discarded organs were misdiagnosed BDH and BDA cases, and one was incorrectly reported as having 90 % microvesicular steatosis during the frozen assessment. We present the clinicopathologic characteristics of liver donors with incidental findings during the pre-transplant evaluation which could lead to unwarranted graft dismissal if misdiagnosed. Additionally, incidental fungal infections can have implications for immunosuppressive therapy and the decision to use or reject the graft.

Glutamine synthetase and hepatocellular carcinoma

Glutamine synthetase (GS) is an enzyme that converts ammonia and glutamate to glutamine using adenosine triphosphate. GS is expressed in the brain, kidney, and liver tissues under normal physiological conditions. GS is involved in abnormal lipid metabolism of the liver by catalyzing de novo synthesis of glutamine, thereby inducing liver inflammation. Metabolic dysfunction-associated steatotic liver diseases (MASLD), such as Metabolic Associated Fatty Liver Disease and Metabolic Associated Steato Hepatitis, are considered risk factors for HCC. GS may also be involved in the development and progression of hepatocellular carcinoma (HCC) through other signaling pathways, including the rapamycin (mTOR) and Wnt/β-catenin signaling pathways. Furthermore, the correct combination of HSP70, GPC3, and GS can improve the accuracy and precision of HCC diagnosis. However, the prognostic value of GS in different HCC populations remains controversial. The expression of GS affects the sensitivity of HCC cells to radiotherapy and chemotherapy. In addition, immunotherapy has been approved for the treatment of advanced HCC. This article delves into the development and application of GS in HCC, laying a theoretical foundation for the subsequent exploration of GS as a potential target for treating HCC.

Ancillary tests for hepatobiliary neoplasms: what we know and what we need to know

Ancillary tests are commonly used in the surgical pathology setting for diagnosing challenging neoplastic diseases of the liver and biliary tract, while histology and clinical correlation remain to be critically important. With continuous discoveries, more and more useful ancillary tests have become available, which can help distinguish between malignant and benign hepatocellular neoplasms, malignant and benign biliary tract entities, and intrahepatic and metastatic carcinomas. This review will focus on existing and emerging biomarkers (such as glutamine synthetase, organic anion transporting polypeptide 1B3, insulin-like growth factor-II mRNA binding protein-3, S100P, SMAD4, enhancer of zeste homolog 2, albumin, hepatocyte nuclear factor-1β, etc.) that can be used for the diagnosis, classification and prognostication of hepatobiliary neoplasms.

Focal Nodular Hyperplasia in the Pediatric Population: A Multicenter Experience

BACKGROUND

Focal nodular hyperplasia (FNH) is a benign liver lesion classically presenting in young females. In children, FNH is rare and its detailed clinicopathologic characteristics remain largely unknown. Furthermore, there are no studies comparing pediatric FNH features to those presenting in adults.

METHODS

In this study, we analyzed a total of 47 FNH cases in pediatric patients (age range: 23 days to 18 years) from 3 centers and compared them to a cohort of 31 FNH cases in adult patients (age range: 20-64 years).

RESULTS

Of the pediatric cases, 13 cases (28%) had a history of a prior malignancy of which 4 were treated with chemoradiation and stem cell transplantation (SCT), 5 with chemoradiation alone and 3 with chemotherapy and SCT. In the pediatric cases 41 (87%) had a central scar and 46 (98%) had fibrous septa. Both pediatric and adult FNH were more common in female patients. Cases in pediatric patients were also significantly associated with larger size (P = .047), absence of dystrophic vessels (P = .001), absence of sinusoidal dilatation (P = .029), pseudoacini formation (P = .013), and steatosis (P = .029).

CONCLUSION

In our experience although most cases of pediatric FNH show the classic histologic features seen in adults, some significant differences exist, and awareness of these findings could aid in the evaluation of these rare cases.

Glutamine Synthetase as a Therapeutic Target for Cancer Treatment

The significance of glutamine in cancer metabolism has been extensively studied. Cancer cells consume an excessive amount of glutamine to facilitate rapid proliferation. Thus, glutamine depletion occurs in various cancer types, especially in poorly vascularized cancers. This makes glutamine synthetase (GS), the only enzyme responsible for de novo synthesizing glutamine, essential in cancer metabolism. In cancer, GS exhibits pro-tumoral features by synthesizing glutamine, supporting nucleotide synthesis. Furthermore, GS is highly expressed in the tumor microenvironment (TME) and provides glutamine to cancer cells, allowing cancer cells to maintain sufficient glutamine level for glutamine catabolism. Glutamine catabolism, the opposite reaction of glutamine synthesis by GS, is well known for supporting cancer cell proliferation via contributing biosynthesis of various essential molecules and energy production. Either glutamine anabolism or catabolism has a critical function in cancer metabolism depending on the complex nature and microenvironment of cancers. In this review, we focus on the role of GS in a variety of cancer types and microenvironments and highlight the mechanism of GS at the transcriptional and post-translational levels. Lastly, we discuss the therapeutic implications of targeting GS in cancer.

Central Hepatic Regenerative Nodules in Alagille Syndrome: A Clinicopathological Review

OBJECTIVE

This review aims to highlight the clinicopathological characteristics and differential diagnosis of central hepatic regenerative nodules (CHRNs) in patients with Alagille syndrome.

METHODS

A review of the literature for cases of CHRNs and their differential diagnoses in patients with Alagille syndrome was performed and the main findings were collated.

RESULTS

Large, regenerative hepatic nodules are seen in approximately 30% of patients with Alagille syndrome. They are thought to be a functional adaptation to vascular changes rather than a neoplastic process. The nodules are typically centrally located, and normal hepatic vasculature coursing through the lesions are noted radiologically. Microscopically, they are characterized by well-circumscribed hepatic lesions with preserved architecture, lesser degrees of fibrosis and relative preservation of interlobular bile ducts compared to the background cirrhotic liver.

CONCLUSION

Regenerative nodules are common in Alagille's syndrome, and should be distinguished from hepatocellular carcinomas and adenomas for appropriate management and prognostication.

Malignant transformation of liver fatty acid binding protein-deficient hepatocellular adenomas: histopathologic spectrum of a rare phenomenon

The molecular classification of hepatocellular adenomas highlights a distinctive genotype-phenotype correlation. Malignant transformation is an exceptionally rare complication of hepatocyte nuclear factor 1α (HNF1A)-inactivated hepatocellular adenomas. This subtype is characterized by loss of liver fatty acid binding protein immunoexpression. In this study, we characterized the histopathologic spectrum of 13 liver fatty acid binding protein-deficient hepatocellular adenoma cases showing malignant transformation from multiple centers. Clinicopathologic characteristics of these patients were evaluated. Stains for reticulin, liver fatty acid binding protein, beta-catenin and glutamine synthetase were applied to these lesions. Moreover, the findings were compared to patients with β-catenin mutated hepatocellular adenoma. Liver fatty acid binding protein-deficient hepatocellular adenomas with borderline features/carcinoma were seen predominantly in females (77%) with an average age of 46 ± 18 years and multiple lesions (77%; five patients with adenomatosis). Meanwhile, β-catenin mutated hepatocellular adenoma patients with malignant transformation were predominantly male (67%, p = 0.018) with single lesion (86%, p = 0.0009). The largest liver fatty acid binding protein-deficient hepatocellular adenoma nodule in each patient ranged from 4 to 15.5 cm. Loss of liver fatty acid binding protein by immunohistochemistry was noted in all adenoma and borderline/carcinoma components. Features of malignant transformation were pseudoglandular architecture (85%), cytologic atypia (85%), architectural atypia (100%) and lack of steatosis (100%). Other findings included myxoid change (39%), peliosis (46%) and sinusoidal dilatation (46%). Molecular studies confirmed somatic inactivation of HNF1A in 3 cases and absence of TERT promotor and exon 3 CTNNB1 mutations in five cases. To summarize, liver fatty acid binding protein-deficient hepatocellular adenoma with malignant transformation is most frequently seen in female patients with multiple lesions. Most of these lesions demonstrate pseudoglandular architecture, cytologic and architectural atypia, with lack of steatosis. The natural history of these lesions is relatively benign with the exception of disease recurrence in 1 patient.

Deficiency of fibroblast growth factor 21 (FGF21) promotes hepatocellular carcinoma (HCC) in mice on a long term obesogenic diet

OBJECTIVE

Non-alcoholic fatty liver (NAFL) associated with obesity is a major cause of liver diseases which can progress to non-alcoholic steatohepatitis, cirrhosis, and hepatocellular carcinoma (HCC). Fibroblast growth factor 21 (FGF21) plays an important role in liver metabolism and is also a potential marker for NAFL. Here we aimed to test the effect of FGF21 deficiency on liver pathology in mice consuming a conventional high fat, high sucrose (HFHS) obesogenic diet for up to 52 weeks.

METHODS

C57BL6 WT and FGF21 KO mice were fed a conventional obesogenic diet and were evaluated at 16 and 52 weeks. Evaluation included metabolic assessment, liver pathology, and transcriptomic analysis.

RESULTS

With consumption of HFHS diet, FGF21 deficient mice (FGF21 KO) develop excess fatty liver within 16 weeks. Hepatic pathology progresses and at 52 weeks FGF21 KO mice show significantly worse fibrosis and 78% of mice develop HCC; in contrast only 6% of WT mice develop HCC. Well differentiated hepatocellular carcinomas in FGF21 KO mice were characterized by expanded hepatic plates, loss of reticulin network, cytologic atypia, and positive immunostaining for glutamine synthetase. Microarray analysis reveals enrichment of several fibroblast growth factor signaling pathways in the tumors.

CONCLUSIONS

In addition to attenuating inflammation and fibrosis in mice under a number of dietary challenges, we show here that FGF21 is required to limit the progression from NAFL to HCC in response to prolonged exposure to an obesogenic diet. The induction of hepatic FGF21 in response to the high fat, high sucrose obesogenic diet may play an important role in limiting progression of liver pathology from NAFL to HCC.

Glypican 3 Overexpression across a Broad Spectrum of Tumor Types Discovered with Functional Genomic mRNA Profiling of a Large Cancer Database

Glypican 3 (GPC3), a membrane-bound heparan sulfate proteoglycan, is overexpressed in approximately 70% to 80% of hepatocellular carcinomas, but is not expressed commonly in healthy tissues. This raised interest in GPC3 as a drug target and several GPC3-targeting drugs are in clinical development. We therefore predicted GPC3 protein overexpression across tumors and validated these predictions. Functional genomic mRNA profiling was applied to the expression profiles of 18,055 patient-derived tumor samples to predict GPC3 overexpression at the protein level in 60 tumor types and subtypes using healthy tissues as reference. For validation, predictions were compared with immunohistochemical (IHC) staining of a breast cancer tissue microarray and literature data reporting IHC GPC3 overexpression in various solid, hematologic, and pediatric tumors. The percentage of samples with predicted GPC3 overexpression was 77% for hepatocellular carcinomas (n = 364), 45% for squamous cell lung cancers (n = 405), and 19% for head and neck squamous cell cancers (n = 344). Breast cancer tissue microarray analysis showed GPC3 expression ranged from 12% to 17% in subgroups based on estrogen receptor and human epidermal growth factor receptor 2 status. In 28 of 34 tumor types for which functional genomic mRNA data could be compared with IHC there was a relative difference of ≤10%. This study provides a data-driven prioritization of tumor types and subtypes for future research with GPC3-targeting therapies.

The Linear ubiquitin chain assembly complex acts as a liver tumor suppressor and inhibits hepatocyte apoptosis and hepatitis

Linear ubiquitination is a key posttranslational modification that regulates immune signaling and cell death pathways, notably tumor necrosis factor receptor 1 (TNFR1) signaling. The only known enzyme complex capable of forming linear ubiquitin chains under native conditions to date is the linear ubiquitin chain assembly complex, of which the catalytic core component is heme-oxidized iron regulatory protein 2 ubiquitin ligase-1-interacting protein (HOIP). To understand the underlying mechanisms of maintenance of liver homeostasis and the role of linear ubiquitination specifically in liver parenchymal cells, we investigated the physiological role of HOIP in the liver parenchyma. To do so, we created mice harboring liver parenchymal cell-specific deletion of HOIP (HoipΔhep mice) by crossing Hoip-floxed mice with albumin-Cre mice. HOIP deficiency in liver parenchymal cells triggered tumorigenesis at 18 months of age preceded by spontaneous hepatocyte apoptosis and liver inflammation within the first month of life. In line with the emergence of inflammation, HoipΔhep mice displayed enhanced liver regeneration and DNA damage. In addition, consistent with increased apoptosis, HOIP-deficient hepatocytes showed enhanced caspase activation and endogenous formation of a death-inducing signaling complex which activated caspase-8. Unexpectedly, exacerbated caspase activation and apoptosis were not dependent on TNFR1, whereas ensuing liver inflammation and tumorigenesis were promoted by TNFR1 signaling.

CONCLUSION

The linear ubiquitin chain assembly complex serves as a previously undescribed tumor suppressor in the liver, restraining TNFR1-independent apoptosis in hepatocytes which, in its absence, is causative of TNFR1-mediated inflammation, resulting in hepatocarcinogenesis. (Hepatology 2017;65:1963-1978).