Fibrolamellar carcinoma: A histologically unique tumor with unique molecular findings

[Hepatocellular carcinoma: Histological and molecular classifications]

Hepatocellular carcinoma (HCC) is the most common primary malignant liver tumour, with a poor prognosis, ranking third for cancer mortality worldwide. HCC is a morphologically and molecularly heterogeneous tumour. This update aims to address this heterogeneity by describing the different histological and molecular subtypes of HCC. Morphologically, eight subtypes have been described according to the WHO classification: steatohepatitic, macrotrabecular massive (MTM), clear cell, chromophobe, scirrhous, fibrolamellar, lymphocyte-rich and neutrophil-rich. Other HCCs are classified as non-specific (not otherwise specified or NOS). These subtypes may be associated with a different prognosis, particularly the MTM, which displays a poorer survival than the other subtypes. Genomically, most HCCs present mutations in the TERT promoter, while other mutations occured later in carcinogenesis, such as TP53 and CTNNB1. TP53 mutated HCCs are associated with a poor prognosis and the MTM subtype. From a transcriptomic standpoint, two classifications are particularly noteworthy, as they are associated with both prognosis (proliferative vs. non-proliferative classification) and clinical, morphological and genomic tumour characteristics (G1-G6 classification). In conclusion, the morphological heterogeneity of HCC, directly linked to molecular heterogeneity, is associated with prognosis. This strongly supports the specification of the different HCC subtypes in our reports.

DNAJB1-PRKACA Fusion Drives Fibrolamellar Liver Cancer through Impaired SIK Signaling and CRTC2/p300-Mediated Transcriptional Reprogramming

SIGNIFICANCE

This work combines functional studies in model systems and examination of human tumor specimens to define a central oncogenic pathway driven by DNAJB1-PRKACA fusions in FLC. DNAJB1-PRKACA-mediated inactivation of the SIK stimulates CRTC2-p300-mediated transcription to drive tumor growth. The findings illuminate pathogenic mechanisms and inform therapeutic development.

Single-cell multi-omic analysis of fibrolamellar carcinoma reveals rewired cell-to-cell communication patterns and unique vulnerabilities

Fibrolamellar carcinoma (FLC) is a rare malignancy disproportionately affecting adolescents and young adults with no standard of care. FLC is characterized by thick stroma, which has long suggested an important role of the tumor microenvironment. Over the past decade, several studies have revealed aberrant markers and pathways in FLC. However, a significant drawback of these efforts is that they were conducted on bulk tumor samples. Consequently, identities and roles of distinct cell types within the tumor milieu, and the patterns of intercellular communication, have yet to be explored. In this study we unveil cell-type specific gene signatures, transcription factor networks, and super-enhancers in FLC using a multi-omics strategy that leverages both single-nucleus ATAC-seq and single-nucleus RNA-seq. We also infer completely rewired cell-to-cell communication patterns in FLC including signaling mediated by SPP1-CD44, MIF-ACKR3, GDF15-TGFBR2, and FGF7-FGFR. Finally, we validate findings with loss-of-function studies in several models including patient tissue slices, identifying vulnerabilities that merit further investigation as candidate therapeutic targets in FLC.

A Case of a Boy With Undiagnosed Fibrolamellar Carcinoma Who Died Due to Severe Hemorrhage From Diaphragm

An 11-year-old boy presented with vomiting and abdominal pain. Ultrasonography and blood tests revealed no abnormalities. He was diagnosed with viral gastroenteritis; however, the following morning, he was found dead in bed. Postmortem examination revealed that a 1,900 mL hemorrhage with strong coagulation from the diaphragm was the cause of death. He had no traumatic episodes, injuries, or a medical history of hemorrhagic diathesis. The presence of a fibrin-like clot indicated coagulation activation; however, most criteria for disseminated intravascular coagulation were not observed. Fibrolamellar carcinoma, a rare hepatocellular carcinoma, was found; however, liver disorder was not estimated based on the pathological findings. In conclusion, the mechanism of hemorrhage could not be explained. Although we were unable to identify the cause of the hemorrhage, we could not completely rule out the possibility that fibrolamellar carcinoma had an unknown influence on the hemorrhage. Given the limited number of studies on fibrolamellar carcinoma, we present a case of a boy with undiagnosed fibrolamellar carcinoma who died due to severe hemorrhage.

FusionVAC22_01: a phase I clinical trial evaluating a DNAJB1-PRKACA fusion transcript-based peptide vaccine combined with immune checkpoint inhibition for fibrolamellar hepatocellular carcinoma and other tumor entities carrying the oncogenic driver fusion

The DNAJB1-PRKACA fusion transcript was identified as the oncogenic driver of tumor pathogenesis in fibrolamellar hepatocellular carcinoma (FL-HCC), also known as fibrolamellar carcinoma (FLC), as well as in other tumor entities, thus representing a broad target for novel treatment in multiple cancer entities. FL-HCC is a rare primary liver tumor with a 5-year survival rate of only 45%, which typically affects young patients with no underlying primary liver disease. Surgical resection is the only curative treatment option if no metastases are present at diagnosis. There is no standard of care for systemic therapy. Peptide-based vaccines represent a low side-effect approach relying on specific immune recognition of tumor-associated human leucocyte antigen (HLA) presented peptides. The induction (priming) of tumor-specific T-cell responses against neoepitopes derived from gene fusion transcripts by peptide-vaccination combined with expansion of the immune response and optimization of immune function within the tumor microenvironment achieved by immune-checkpoint-inhibition (ICI) has the potential to improve response rates and durability of responses in malignant diseases. The phase I clinical trial FusionVAC22_01 will enroll patients with FL-HCC or other cancer entities carrying the DNAJB1-PRKACA fusion transcript that are locally advanced or metastatic. Two doses of the DNAJB1-PRKACA fusion-based neoepitope vaccine Fusion-VAC-XS15 will be applied subcutaneously (s.c.) with a 4-week interval in combination with the anti-programmed cell death-ligand 1 (PD-L1) antibody atezolizumab starting at day 15 after the first vaccination. Anti-PD-L1 will be applied every 4 weeks until end of the 54-week treatment phase or until disease progression or other reason for study termination. Thereafter, patients will enter a 6 months follow-up period. The clinical trial reported here was approved by the Ethics Committee II of the University of Heidelberg (Medical faculty of Mannheim) and the Paul-Ehrlich-Institute (P-00540). Clinical trial results will be published in peer-reviewed journals.

Trial registration numbers

EU CT Number: 2022-502869-17-01 and ClinicalTrials.gov Registry (NCT05937295).

DNAJB1-PRKACA fusion protein-regulated LINC00473 promotes tumor growth and alters mitochondrial fitness in fibrolamellar carcinoma

Fibrolamellar carcinoma (FLC) is a rare liver cancer that disproportionately affects adolescents and young adults. Currently, no standard of care is available and there remains a dire need for new therapeutics. Most patients harbor the fusion oncogene DNAJB1-PRKACA (DP fusion), but clinical inhibitors are not yet developed and it is critical to identify downstream mediators of FLC pathogenesis. Here, we identify long noncoding RNA LINC00473 among the most highly upregulated genes in FLC tumors and determine that it is strongly suppressed by RNAi-mediated inhibition of the DP fusion in FLC tumor epithelial cells. We show by loss- and gain-of-function studies that LINC00473 suppresses apoptosis, increases the expression of FLC marker genes, and promotes FLC growth in cell-based and in vivo disease models. Mechanistically, LINC00473 plays an important role in promoting glycolysis and altering mitochondrial activity. Specifically, LINC00473 knockdown leads to increased spare respiratory capacity, which indicates mitochondrial fitness. Overall, we propose that LINC00473 could be a viable target for this devastating disease.

SEPT9 Expression in Hepatic Nodules: An Immunohistochemical Study of Hepatocellular Neoplasm and Metastasis

The methylated SEPT9 DNA ( mSEPT9 ) in plasma is a US Food and Drug Administration (FDA)-approved screening biomarker in colorectal cancer and is emerging as a promising diagnostic and prognostic biomarker in hepatocellular carcinoma (HCC). We evaluated the SEPT9 protein expression by immunohistochemistry (IHC) in various hepatic tumors from 164 hepatectomies and explants. Cases diagnosed as HCC (n=68), hepatocellular adenoma (n=31), dysplastic nodule (n=24), and metastasis (n=41) were retrieved. SEPT9 stain was performed on representative tissue blocks showing tumor/liver interface. For HCC, archived IHC (SATB2, CK19, CDX2, CK20, and CDH17) slides were also reviewed. The findings were correlated with demographics, risk factors, tumor size, alpha fetoprotein levels at diagnosis, T stage and oncologic outcomes, with significance defined as P <0.05. Percentage of SEPT9 positivity differed significantly among hepatocellular adenoma (3%), dysplastic nodule (0%), HCC (32%), and metastasis (83%, P <0.001). Compared with patients with SEPT9- HCC, those with SEPT9+ HCC were older (70 vs. 63 y, P =0.01). The extent of SEPT9 staining correlated with age ( rs =0.31, P =0.01), tumor grade ( rs =0.30, P =0.01), and extent of SATB2 staining ( rs =0.28, P =0.02). No associations were found between SEPT9 staining and tumor size, T stage, risk factors, CK19, CDX2, CK20, or CDH17 expression, alpha fetoprotein levels at diagnosis, METAVIR fibrosis stage, and oncologic outcome in the HCC cohort. SEPT9 is likely implicated in liver carcinogenesis in a HCC subset. Similar to mSEPT9 DNA measurement in liquid biopsies, SEPT9 staining by IHC may prove helpful as an adjunct diagnostic biomarker with potential prognostic ramifications.

A Multidisciplinary Approach to the Management of Fibrolamellar Carcinoma: Current Perspectives and Future Prospects

Fibrolamellar carcinoma (FLC) is a rare primary liver tumor affecting predominantly younger and otherwise healthy patients. Typically, FLC presents with advanced disease due to the paucity of typical symptoms and no history of underlying liver disease. Depending on tumor characteristics and the patient's general condition, surgical treatment is the most promising treatment modality. Aggressive resection and liver transplantation have been utilized and are presently indispensable curative treatment options. Under certain circumstances surgical resection is also possible for metachronous metastases or local recurrence. Recent tumor biology discoveries have contributed to improved diagnostic specificity and systemic treatment options.

Human liver organoids for disease modeling of fibrolamellar carcinoma

Fibrolamellar carcinoma (FLC) is a rare, often lethal, liver cancer affecting adolescents and young adults, for which there are no approved therapeutics. The development of therapeutics is hampered by a lack of in vitro models. Organoids have shown utility as a model system for studying many diseases. In this study, tumor tissue and the adjacent non-tumor liver were obtained at the time of surgery. The tissue was dissociated and grown as organoids. We developed 21 patient-derived organoid lines: 12 from metastases, three from the liver tumor and six from adjacent non-tumor liver. These patient-derived FLC organoids recapitulate the histologic morphology, immunohistochemistry, and transcriptome of the patient tumor. Patient-derived FLC organoids were used in a preliminary high-throughput drug screen to show proof of concept for the identification of therapeutics. This model system has the potential to improve our understanding of this rare cancer and holds significant promise for drug testing and development.

Chemical, Molecular, and Single-nucleus Analysis Reveal Chondroitin Sulfate Proteoglycan Aberrancy in Fibrolamellar Carcinoma

Fibrolamellar carcinoma (FLC) is an aggressive liver cancer with no effective therapeutic options. The extracellular environment of FLC tumors is poorly characterized and may contribute to cancer growth and/or metastasis. To bridge this knowledge gap, we assessed pathways relevant to proteoglycans, a major component of the extracellular matrix. We first analyzed gene expression data from FLC and nonmalignant liver tissue (n = 27) to identify changes in glycosaminoglycan (GAG) biosynthesis pathways and found that genes associated with production of chondroitin sulfate, but not other GAGs, are significantly increased by 8-fold. We then implemented a novel LC/MS-MS based method to quantify the abundance of different types of GAGs in patient tumors (n = 16) and found that chondroitin sulfate is significantly more abundant in FLC tumors by 6-fold. Upon further analysis of GAG-associated proteins, we found that versican (VCAN) expression is significantly upregulated at the mRNA and protein levels, the latter of which was validated by IHC. Finally, we performed single-cell assay for transposase-accessible chromatin sequencing on FLC tumors (n = 3), which revealed for the first time the different cell types in FLC tumors and also showed that VCAN is likely produced not only from FLC tumor epithelial cells but also activated stellate cells. Our results reveal a pathologic aberrancy in chondroitin (but not heparan) sulfate proteoglycans in FLC and highlight a potential role for activated stellate cells.

Significance

This study leverages a multi-disciplinary approach, including state-of-the-art chemical analyses and cutting-edge single-cell genomic technologies, to identify for the first time a marked chondroitin sulfate aberrancy in FLC that could open novel therapeutic avenues in the future.

Multiomic analysis of microRNA-mediated regulation reveals a proliferative axis involving miR-10b in fibrolamellar carcinoma

Fibrolamellar carcinoma (FLC) is an aggressive liver cancer primarily afflicting adolescents and young adults. Most patients with FLC harbor a heterozygous deletion on chromosome 19 that leads to the oncogenic gene fusion, DNAJB1-PRKACA. There are currently no effective therapeutics for FLC. To address that, it is critical to gain deeper mechanistic insight into FLC pathogenesis. We assembled a large sample set of FLC and nonmalignant liver tissue (n = 52) and performed integrative multiomic analysis. Specifically, we carried out small RNA sequencing to define altered microRNA expression patterns in tumor samples and then coupled this analysis with RNA sequencing and chromatin run-on sequencing data to identify candidate master microRNA regulators of gene expression in FLC. We also evaluated the relationship between DNAJB1-PRKACA and microRNAs of interest in several human and mouse cell models. Finally, we performed loss-of-function experiments for a specific microRNA in cells established from a patient-derived xenograft (PDX) model. We identified miR-10b-5p as the top candidate pro-proliferative microRNA in FLC. In multiple human cell models, overexpression of DNAJB1-PRKACA led to significant upregulation of miR-10b-5p. Inhibition of miR-10b in PDX-derived cells increased the expression of several potentially novel target genes, concomitant with a significant reduction in metabolic activity, proliferation, and anchorage-independent growth. This study highlights a potentially novel proliferative axis in FLC and provides a rich resource for further investigation of FLC etiology.

A framework for fibrolamellar carcinoma research and clinical trials

Fibrolamellar carcinoma (FLC), a rare, lethal hepatic cancer, occurs primarily in adolescents and young adults. Unlike hepatocellular carcinoma, FLC has no known association with viral, metabolic or chemical agents that cause cirrhosis. Currently, surgical resection is the only treatment demonstrated to achieve cure, and no standard of care exists for systemic therapy. Progress in FLC research illuminates a transition from an obscure cancer to one for which an interactive community seems poised to uncover fundamental mechanisms and initiate translation towards novel therapies. In this Roadmap, we review advances since the seminal discovery in 2014 that nearly all FLC tumours express a signature oncogene (DNAJB1-PRKACA) encoding a fusion protein (DNAJ-PKAc) in which the J-domain of a heat shock protein 40 (HSP40) co-chaperone replaces an amino-terminal segment of the catalytic subunit of the cyclic AMP-dependent protein kinase (PKA). Important gains include increased understanding of oncogenic pathways driven by DNAJ-PKAc; identification of potential therapeutic targets; development of research models; elucidation of immune mechanisms with potential for the development of immunotherapies; and completion of the first multicentre clinical trials of targeted therapy for FLC. In each of these key areas we propose a Roadmap for future progress.

Hepatocellular Carcinoma: Does the Background Liver With or Without Cirrhosis Matter?

OBJECTIVES

The pathologic differences between hepatocellular carcinoma (HCC) arising in noncirrhotic and cirrhotic livers have not been well studied.

METHODS

We performed a retrospective analysis of 378 HCC cases (95 in noncirrhotic, 283 in cirrhotic livers) from pathology archives (2010-2017).

RESULTS

Patients without cirrhosis were more likely to have hepatitis B (13.68% vs 2.83%, P < .001) or no known liver disease (30.53% vs 4.24%, P < .001), while hepatitis C was more common in patients with cirrhosis (65.72% vs 30.53%, P < .001). HCCs in noncirrhotic livers were larger in size (P < .001); were more likely to have a macrotrabecular histologic pattern (13.68% vs 4.95%, P < .01); were more likely to have fibrolamellar (3.16% vs 0%, P = .02), macrotrabecular-massive (13.68% vs 6.01%, P = .03), and clear cell (16.84% vs 6.71%, P < .01) subtypes; have a higher histologic grade (P < .01); be anaplastic tumor cells (P < .001); have a higher rate of vascular invasion (P < .01); and have a higher tumor stage (P = .04).

CONCLUSIONS

The findings indicate that HCCs in noncirrhotic livers demonstrate a larger tumor size; have a more macrotrabecular histologic pattern; have fibrolamellar, macrotrabecular-massive, and clear cell subtypes; have a higher tumor grade and stage; have a higher rate of vascular invasion; and have more anaplastic tumor cells compared with cirrhotic livers. Further studies to explore different pathways that promote oncogenesis in noncirrhotic livers are needed to better understand the pathogenesis of HCC.

Clinicopathological and molecular characterization of chromophobe hepatocellular carcinoma

BACKGROUND AND AIMS

Chromophobe hepatocellular carcinoma (HCC) is a newly included subtype of HCC in the 5th edition of the WHO classification with distinctive histological features (chromophobic cytoplasm with anaplastic nuclei and pseudocyst formation) and is strongly associated with the alternative lengthening of telomeres (ALT) phenotype. However, the clinicopathologic characterization and molecular features of chromophobe HCC are unknown.

METHODS

To comprehensively characterize chromophobe HCC, whole exome sequencing, copy number variation, and transcriptomic analyses were performed in 224 surgically resected HCC cases. Additionally, telomere-specific fluorescence in situ hybridization was used to assess ALT. These genomic profiles and ALT status were compared with clinicopathological features among subtypes of HCC, particularly chromophobe HCC and conventional HCC.

RESULTS

Chromophobe HCC was observed in 10.3% (23/224) cases and, compared to conventional HCC, was more frequent in females (P = .023). The overall and recurrence-free survival outcomes were similar between patients with chromophobe HCC and conventional HCC. However, chromophobe HCC displayed significantly more upregulated genes involving cell cycle progression and DNA repair. Additionally, ALT was significantly enriched in chromophobe HCC (87%; 20/23) compared to conventional HCC (2.2%, 4/178; P < .001). Somatic mutations in ALT-associated genes, including ATRX, SMARCAL1, FANCG, FANCM, SP100, TSPYL5, and RAD52 were more frequent in chromophobe HCC (30.4%, 7/23 cases) compared to conventional HCC (11.8%, 21/178 cases; P = .024).

CONCLUSIONS

Chromophobe HCC is a unique subtype of HCC with a prevalence of ~10%. Compared to conventional HCC, chromophobe HCC is associated with female predominance and ALT, although overall and recurrence-free outcomes are similar to conventional HCC.

Pediatric Liver Tumors: Updates in Classification

Malignant primary liver tumors are rare in children. Yet a wide histologic spectrum is seen, particularly in hepatoblastoma, the most common malignant liver tumor in children. Furthermore, there can be significant morphologic overlap with hepatocellular carcinoma, the second most common pediatric liver malignancy, and tumors with hybrid features of hepatoblastoma and hepatocellular carcinoma are also reported (currently placed in the provisional category of malignant hepatocellular neoplasm, not otherwise specified). This review provides detailed morphologic descriptions and updates in the evolving clinical context of these tumors, and presents recent molecular advances that may further help in accurate classification of these tumors, which is critical in their management.

Aberrant expression of SATB2, CDX2, CDH17 and CK20 in hepatocellular carcinoma: a pathological, clinical and outcome study

AIMS

Data regarding expression of intestinal markers in hepatocellular carcinoma (HCC) are limited. We determined the clinicopathological associations of cytokeratin (CK)19, a progenitor liver epithelial cell marker as well as biliary epithelial marker, and intestinal immunohistochemical markers expression in HCC and assessed their prognostic value.

METHODS AND RESULTS

Tissue sections and/or tissue microarrays (TMAs) from 202 known HCCs were immunostained using CK19, CK20, CDH17, CDX2 and SATB2 antibodies. Haematoxylin and eosin (H&E)-stained slides were reviewed for tumour grading. Clinical and oncological outcomes were retrieved. Associations of staining with clinicopathological features and survival outcomes were evaluated. CK19, CK20, CDH17, CDX2 and SATB2 were positive in 12.8, 5.4, 10.3, 8.6 and 59.9%, respectively. All but SATB2 were strongly associated with higher tumour grade and AFP levels > 400 ng/ml (P < 0.05). CK19-positive HCC were more likely to express CDX2 (P = 0.001), CDH17 (P < 0.001) and/or CK20 (P = 0.012). CK20, CDX2 and CDH17 co-expression was seen in five cases (2.5%). CK19 and SATB2 positivity, tumour size ≥ 5 cm, background cirrhosis, AFP > 400 ng/ml and having no treatment were associated with decreased overall survival by log-rank test and univariable proportional hazards regression. However, in a multivariable model, CK19 and SATB2 positivity were not independent predictors of decreased survival while their association with known poor prognosticators in HCC was evident.

CONCLUSIONS

HCC can express markers of intestinal differentiation. This phenotypical aberrancy correlates with variable clinicopathological parameters, some of which are independent predictors of poor survival.

Pathologic and molecular features of hepatocellular carcinoma: An update

Morphological diversity and several new distinct pathologic subtypes of hepatocellular carcinoma (HCC) are now well-recognized. Recent advances in tumor genomics and transcriptomics have identified several recurrent somatic/genetic alterations that are closely related with histomorphological subtypes and have therefore, greatly improved our understanding of HCC pathogenesis. Pathologic subtyping allows for a diagnosis which is clinically helpful and can have important implication in patient prognostication as some of these subtypes are extremely aggressive with vascular invasion, early recurrence, and worst outcomes. Several targeted treatments are now being considered in HCC, and the reporting of subtypes may be quite useful for personalized therapeutic purpose. This manuscript reviews the recently identified histomorphological subtypes and molecular alterations in HCC.

An update on subtypes of hepatocellular carcinoma: From morphology to molecular

The morphologic spectrum of hepatocellular carcinoma (HCC) is quite broad. While in about one-third of cases, the neoplasms can be categorized into meaningful subtypes based on morphology, a vast majority of these neoplasms are morphologically heterogeneous. With extensive tumor profiling, data has begun to emerge which can correlate specific morphologic features with underlying molecular signatures. A true morphologic subtype not only has reproducible H & E features, further supported by specific immunohistochemical or molecular signatures, but also has specific clinical implications and prognostic associations. Eight such morphologic subtypes are recognized by the 2019 WHO classification of tumors with a few more additional subtypes described in the literature. The goal of this review is to familiarize the reader with the morphologic subtypes and elaborate on the clinical and molecular associations of these neoplasms.

Inhibition of vitamin D analog eldecalcitol on hepatoma in vitro and in vivo

Hepatoma is a serious liver cancer with high morbidity and mortality. Eldecalcitol (ED-71), a vitamin D analog, is extensively used as anti-cancer agent in vitro. Hepatocellular carcinoma cell, SMMC-7721 cell lines were used in this study. Transwell assay, cell apoptosis and cell cycle detection assays were investigated after treatment with ED-71 and phosphate buffered saline (PBS) as control. Sizes of tumors were measured after ED-71 treatment in a mouse model. E-cadherin and Akt gene expressions were detected by real-time PCR (RT-PCR). The results showed that cell invasion and migration were decreased markedly after ED-71 treatment compared to control group. Cell cycle detection showed that the G2 stage was 13.18% and total S-stage was 41.16% in the ED-71 group and G2 stage: 22.88%, total S-stage: 27.34% in the control group. Cell apoptosis rate was promoted in the ED-71 group. Size of the tumors reduced more after the ED-71 treatment than the PBS treatment in mice. ED-71 markedly inhibited the expression of Akt and E-cadherin, either detected by immunohistochemistry or RT-PCR. ED-71 treatment can inhibit the hepatoma agent proliferation by increasing the E-cadherin expression and decreasing Akt expression. Therefore, these findings provide novel evidence that ED-71 can be used as an anti-hepatoma agent.

Fibrolamellar Carcinoma With Predominantly Pseudoglandular Architecture: A Potential Diagnostic Pitfall

Biopsies of liver mass lesions are encountered frequently in general surgical pathology practice. The clinical differential diagnosis is typically hepatocellular carcinoma (HCC) versus metastatic adenocarcinoma. There are a variety of HCC variants that show a range of morphological appearances. The presence of malignant glands in the liver prompts the pathologist to consider adenocarcinoma, either metastatic or primary intrahepatic cholangiocarcinoma. It is important to remember that some variant patterns of HCC can show pseudoglandular growth. In this article, we present a case of fibrolamellar carcinoma that showed predominantly pseudoglandular growth to highlight the importance of a systematic approach and the routine use of a panel of immunohistochemical stains (HepPar1, CK7, and CD68).

Pearls and pitfalls in magnetic resonance imaging of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most common primary hepatic malignancy, which usually arises in cirrhotic liver. When the typical enhancement pattern, consisting of late arterial hyperenhancement followed by washout, is present in nodules larger than 1 cm, HCC can be confidently diagnosed without the need for tissue biopsy. Nevertheless, HCC can display an atypical enhancement pattern, either as iso or hypovascular lesion, or hypervascular lesion without washout. Not only the enhancement pattern of HCC could be atypical, but also a variety of histological types of HCC, such as steatotic, scirrhous, fibrolamellar, or combined hepatocellular-cholangiocellular carcinoma could raise diagnostic dilemmas. In addition, distinct morphological types of HCC or different growth pattern can occur. Awareness of these atypical and rare HCC presentations on magnetic resonance imaging is important for accurate differentiation from other focal liver lesions and timely diagnosis, which allows optimal treatment of patients.

DNAJB1-PRKACA-positive metastatic fibrolamellar carcinoma with unknown primary in a pediatric patient

Fibrolamellar carcinoma (FLC) is a rare variant of hepatocellular carcinoma, occurring in children and young adults without underlying liver disease. The diagnosis is based on morphological characteristics of the tumor, supplemented by immunohistochemistry and/or genetic testing. Recently, the presence of a characteristic DNAJB1-PRKACA fusion gene has been associated with FLC. Herein, we report a case of FLC presenting as peritoneal carcinomatosis in a 14-year-old female. Interestingly, no liver tumor was seen on imaging, and an alternative possibility is that the tumor arose outside the liver as a hepatoid carcinoma with fibrolamellar features.

Single-Cell RNA Sequencing Identifies Yes-Associated Protein 1-Dependent Hepatic Mesothelial Progenitors in Fibrolamellar Carcinoma

Fibrolamellar carcinoma (FLC) is characterized by in-frame fusion of DnaJ heat shock protein family (Hsp40) member B1 (DNAJB1) with protein kinase cAMP-activated catalytic subunit α (PRKACA) and by dense desmoplasia. Surgery is the only effective treatment because mechanisms supporting tumor survival are unknown. We used single-cell RNA sequencing to characterize a patient-derived FLC xenograft model and identify therapeutic targets. Human FLC cells segregated into four discrete clusters that all expressed the oncogene Yes-associated protein 1 (YAP1). The two communities most enriched with cells coexpressing FLC markers [CD68, A-kinase anchoring protein 12 (AKAP12), cytokeratin 7, epithelial cell adhesion molecule (EPCAM), and carbamoyl palmitate synthase-1] also had the most cells expressing YAP1 and its proproliferative target genes (AREG and CCND1), suggesting these were proliferative FLC cell clusters. The other two clusters were enriched with cells expressing profibrotic YAP1 target genes, ACTA2, ELN, and COL1A1, indicating these were fibrogenic FLC cells. All clusters expressed the YAP1 target gene and mesothelial progenitor marker mesothelin, and many mesothelin-positive cells coexpressed albumin. Trajectory analysis predicted that the four FLC communities were derived from a single cell type transitioning among phenotypic states. After establishing a novel FLC cell line that harbored the DNAJB1-PRKACA fusion, YAP1 was inhibited, which significantly reduced expression of known YAP1 target genes as well as cell growth and migration. Thus, both FLC epithelial and stromal cells appear to arise from DNAJB1-PRKACA fusion in a YAP1-dependent liver mesothelial progenitor, identifying YAP1 as a target for FLC therapy.

Deleted in Liver Cancer 2 (DLC2) protein expression in hepatocellular carcinoma

Deleted in Liver Cancer (DLC) proteins belong to the family of RhoGAPs and are believed to operate as negative regulators of the Rho family of small GTPases. So far, the role of the first identified member from the DLC family, DLC1, was established as a tumor suppressor in hepatocellular carcinoma. The function of its close family relative, DLC2 is unequivocal. In the present study we attempted to determine whether the loss of DLC2 is a common feature of hepatocellular carcinoma tissue. We examined two types of hepatocellular carcinomatypical and fibrolamellar one. Our analysis revealed that DLC2 protein is not diminished in cancer tissue when compared to non-cancerous liver specimens. What is more, we observed DLC2 to be more abundantly expressed in cancer tissue, particularly in tumors with the inflammation background. In addition, we found that DLC2 gene status was diploid in virtually all tumor samples examined. Our results indicate that DLC2 is not diminished in hepatocellular carcinoma cells. It appears that members of the DLC family, although structurally highly related, may function differently in cancer cells.

Acquired ornithine transcarbamylase deficiency in pediatric and adolescent patients with fibrolamellar hepatocellular carcinoma

Ornithine transcarbamylase deficiency (OTCD) disrupts the metabolic pathway responsible for converting nitrogenous waste to urea, allowing for excretion. When impaired, ammonia levels accumulate in the blood resulting in severe, sometimes life-threatening toxicities. Abnormalities of the urea cycle are often inherited, though there are some rarer acquired forms. We describe two cases of acquired OTCD in pediatric patients with fibrolamellar hepatocellular carcinoma (FL-HCC). We detail its presentation and management, explore potential underlying pathophysiology, and propose a practice change to optimize care of FL-HCC patients.

Fibrolamellar carcinoma in the Carney complex: PRKAR1A loss instead of the classic DNAJB1-PRKACA fusion

Fibrolamellar carcinomas are characterized by activation of protein kinase A, a kinase composed of catalytic and regulatory subunits. PRKACA encodes a catalytic subunit of protein kinase A, and almost all fibrolamellar carcinomas have a heterozygous 400-kb deletion that leads to the fusion of DNAJB1 and PRKACA. The resulting DNAJB1-PRKACA fusion transcript is believed to activate protein kinase A by dysregulation of the catalytic portion of the protein. In contrast, PRKAR1A encodes one of the regulatory subunits of protein kinase A. We hypothesized that loss of function of this regulatory unit could also lead to protein kinase A activation and thus to fibrolamellar carcinoma. Because PRKAR1A mutations underlie the Carney complex, we searched for liver tumors in individuals with the Carney complex. We identified 3 individuals with fibrolamellar carcinomas and a personal history of the Carney complex. All three tumors displayed the typical morphology of fibrolamellar carcinoma and were positive for arginase, cytokeratin 7, and cluster of differentiation 68. Fluorescence in situ hybridization was negative for PRKACA rearrangements. However, PRKAR1A sequencing identified pathogenic mutations in two of two cases with successful sequencing. In addition, all three cases were negative for PRKAR1A protein expression, consistent with inactivation of this key regulatory unit of protein kinase A. We also identified one additional fibrolamellar carcinoma in an individual without a documented history of the Carney complex who was negative for PRKACA rearrangements but had loss of PRKAR1A protein expression as well as PRKAR1A mutations.

CONCLUSION

Fibrolamellar carcinoma can be part of the Carney complex; in this setting, fibrolamellar carcinomas have inactivating PRKAR1A mutations instead of the DNAJB1-PRKACA fusion gene found in sporadic fibrolamellar carcinomas, providing an alternate means for activation of protein kinase A. (Hepatology 2017).

A first case of hepatocellular carcinoma in the baboon (Papio spp.) placenta

We present a case of hepatocellular carcinoma (HCC) in the placenta of healthy baboon (Papio spp.). Grossly, the fetal, maternal, and placental tissues were unremarkable. Histologically, the placenta contained an unencapsulated, poorly demarcated, infiltrative, solidly cellular neoplasm composed of cells that resembled hepatocytes. The neoplastic cells were diffusely positive for vimentin and focally positive for Ae1/Ae3, Arginase -1, glutamine synthetase, and CD10, and negative for ER, vascular markers (CD31 and D240), S100, glypican, C-reactive protein, FABP, desmin, and beta-catenin; INI1 positivity was similar to non-neoplastic tissues. The case likely represents a unique subtype of HCC.

Fibrolamellar Carcinoma: A Concise Review

Fibrolamellar carcinoma is a rare primary hepatocellular malignancy arising in noncirrhotic livers of young individuals. Patients commonly present with a large solitary liver mass and nonspecific symptoms. Characteristic histologic features include large polygonal cells with oncocytic cytoplasm and prominent nucleoli separated into trabeculae and cords by dense parallel bands of collagen. Important differential diagnoses include classical hepatocellular carcinoma and intrahepatic cholangiocarcinoma, which may be distinguished by a judicious panel of immunohistochemical studies, including cytokeratin 7, CD68, and hepatocyte paraffin 1 (HepPar-1). In addition, fibrolamellar carcinomas are characterized by activation of protein kinase A. Prognosis of fibrolamellar carcinoma is similar to classical hepatocellular carcinoma occurring in the absence of liver cirrhosis and is strongly correlated with tumor resectability. Other treatment options include liver transplant, chemotherapy, and hepatic artery embolization. In this article, we review the clinical features, gross and microscopic pathology, molecular genetics, differential diagnosis, treatment, and prognosis of this rare and interesting tumor.

Update on Ancillary Testing in the Evaluation of High-Grade Liver Tumors

Tissue diagnosis is the gold standard for mass lesions of the liver, but needle core biopsies may sometimes prove challenging. Presented here is a review of a panel of immunohistochemical stains, including hepatocyte in paraffin 1, arginase-1, polyclonal carcinoembryonic antigen, CD10, bile salt export pump, glypican-3, as well as in situ hybridization for albumin RNA, to establish hepatocellular origin in cases in which hepatocellular carcinoma is suspected but the sample is limited or the morphology is challenging, as it may be with cases of scirrhous, fibrolamellar carcinoma, intrahepatic cholangiocarcinoma, and combined hepatocellular-cholangiocarcinoma.