Molecular pathogenesis of focal nodular hyperplasia and hepatocellular adenoma

Hepatocellular adenoma and focal nodular hyperplasia: value of gadoxetic acid-enhanced MR imaging in differential diagnosis

PURPOSE

To retrospectively evaluate the utility of gadoxetic acid-enhanced magnetic resonance (MR) imaging in the differential diagnosis of hepatocellular adenoma (HCA) and focal nodular hyperplasia (FNH).

MATERIALS AND METHODS

This study had institutional review board approval; the requirement for informed consent was waived. Eighty-two patients (58 patients with FNH and 24 patients with HCAs) with 111 lesions were included in the study. There were 74 female patients and eight male patients (mean age, 41.9 years±13.2 [standard deviation]; age range, 11-78 years). Two readers reviewed all images in terms of signal intensity (SI) features on unenhanced, dynamic, and hepatobiliary phase images. For quantitative analysis, contrast enhancement ratio (CER), lesion-to-liver contrast (LLC), and SI ratio on dynamic and hepatobiliary phase images were calculated.

RESULTS

The CER of FNH in the arterial phase (mean, 94.3%±33.2) was significantly higher than that of HCAs (mean, 59.3%±28.1) (P<.0001). During the hepatobiliary phase, the LLC of FNH showed minimally positive values (mean, 0.05±0.01) and that of HCAs demonstrated strong negative values (mean, -0.67±0.24) (P<.0001). The area under the receiver operating characteristic curve of the hepatobiliary phase SI ratio for differentiation of the two tumors was 0.97, and a sensitivity of 92% and specificity of 91% were found with a cutoff value of 0.87. Among six FNH lesions that showed atypical hypointensity during the hepatobiliary phase, four had a large central scar, one contained a substantial fat component, and one had abundant radiating fibrous septa. Three HCAs were isointense during the hepatobiliary phase owing to severe hepatic steatosis.

CONCLUSION

Gadoxetic acid-enhanced MR imaging facilitates the differentiation of FNH from HCA.

[Focal nodular hyperplasia in a 12-year-old boy: case report and considerations]

BACKGROUND

Focal nodular hyperplasia (FNH) is a benign hepatic tumor of unknown origin. It is only observed rarely in children (approximately 1-2% of all pediatric liver tumors).

CASE REPORT

A 12-year-old boy who suffered from infectious mononucleosis with liver involvement and hepatomegaly underwent a sonographic scan of the liver at an external hospital 3 months after the infection disappeared which revealed a tumor of the left hepatic lobule. Subsequent further examination (abdominal CT and MRT scans) confirmed the diagnosis of a highly vascularized mass about 10 cm in diameter, suspicious for FNH. Due to the high vascularization no biopsy was performed. A preoperative angiographic coiling and complete surgical resection was carried out because of the size and morphologic uncertainty. The diagnosis of FNH was confirmed by histological examination. The annual sonographic examination at follow-up has been uneventful for a 4-year period.

CONCLUSIONS

Due to the rarity the diagnosis of FNH in children can be difficult leading to differential diagnostic problems. Due to the risk of bleeding in larger size tumors a biopsy is a point of controversy. Complete resection and histopathological examination of FNHs in childhood is a mandatory therapeutic option, which may be indicated in large tumors or, as in the present case tumors of uncertain biological behaviour.

Overview of hepatocellular adenoma in Japan

Hepatocellular adenoma (HCA) is generally a benign hepatocellular tumor arising in a nonfibrotic/cirrhotic liver, and recently four major subgroups were identified based on genotype and phenotype classification from Europe. HCA is rare in Asian countries including Japan, and there have been few studies regarding the subgroups of HCA in Japan. We surveyed subgroups of HCA in 13 patients (7 women) in Japan, based on the phenotypic classification. As results, we identified 2 hepatocyte nuclear factor (HNF) 1α-inactivated HCAs (15%), two β-catenin-activated HCAs (15%), 5 inflammatory HCAs (39%), and 4 unclassified HCAs (29%). The use of oral contraceptives was found only in 2 unclassified HCAs (29%). Rather low percentage of female patients and use of oral contraceptives appear to be common clinicopathological features in Japan and also East Asian countries. Furthermore, a group of possible inflammatory HCAs characterized by strong immunoreactivity for serum amyloid A (SAA) was found in patients with alcoholic cirrhosis. The inflammatory HCA/SAA-positive hepatocellular neoplasm in alcoholic cirrhosis may be a new entity of HCA, which may have potential of malignant transformation. Further studies are needed to clarify genetic changes, monoclonality, and pathogenesis of this new type of hepatocellular neoplasm.

Can a decision-making model be justified in the management of hepatocellular adenoma?

During recent years, there was a great development in the area of hepatocellular adenomas (HCA), especially regarding the pathological subtype classification, radiological imaging and management during pregnancy. This review discusses the current knowledge about diagnosis and treatment modalities of HCA and proposes a decision-making model for HCA. A Medline search of studies relevant to epidemiology, histopathology, complications, imaging and management of HCA lesions was undertaken. References from identified articles were hand-searched for further relevant articles.

High-b-value diffusion-weighted MR imaging of benign hepatocellular lesions: quantitative and qualitative analysis

PURPOSE

To analyze the signal intensity (SI) of benign hepatocellular lesions in high-b-value diffusion-weighted (DW) magnetic resonance (MR) images and to compare the apparent diffusion coefficient (ADC) values of focal nodular hyperplasias (FNHs) with those of hepatocellular adenomas (HCAs).

MATERIALS AND METHODS

This retrospective study was approved by institutional review board, with waiver of informed consent. Inclusion criteria were consecutive patients with diagnosed FNH or HCA who underwent MR imaging with a DW sequence of the liver at three b values, 0, 150, and 600 sec/mm2. The final study population included 67 patients (seven men, 60 women) with 90 hepatocellular lesions (54 FNHs, 36 HCAs). The mean ADC was compared between the lesions and the liver. Receiver operating characteristic analysis was performed to evaluate the diagnostic value of ADC for differentiating HCAs and FNHs.

RESULTS

The mean ADC value of all FNHs and HCAs was significantly lower than that of the liver (P=.004). An ADC ratio below 15% was observed in 50 of 54 (93%) FNHs and in 29 of 36 (81%) HCAs. The mean ADC value of FNHs was significantly higher than that of HCAs (P<.001). The area under the receiver operating characteristic curve was 0.760. With a cutoff value of 1.37×10(-3) mm2/sec, the sensitivity and specificity for differentiating HCA from FNH were 70% and 76%, respectively. There was no significant difference in ADC values between HCA subtypes. The SI of most FNHs and HCAs (78 of 90, 87%) increased with increasing b values, whereas none showed a decrease in SI with increasing b values. When the DW MR criteria for benign and malignant liver tumors were applied, 44 of 90 (49%) lesions would have been considered malignant lesions, whereas the other lesions (46 of 90, 51%) would have been considered indeterminate.

CONCLUSION

On DW MR images, benign hepatocellular lesions often show findings that suggest restricted diffusion.

Characterization of hepatocellular adenoma based on the phenotypic classification: The Kanazawa experience

AIM

  Hepatocellular adenoma (HCA) represents a heterogeneous entity, and recently four major subgroups were identified based on genotype and phenotype classification from Europe. HCA is rare in Asian countries including Japan and there has been no study regarding the subgroups of HCA in Japan.

METHODS

  We took advantage of the reported genotype/phenotype classification to analyze 14 HCA (seven women) in Japan.

RESULTS

  We identified one hepatocyte nuclear factor (HNF)1α-inactivated HCA (one woman), two β-catenin-activated HCA (one woman), seven inflammatory HCA (IHCA, two women); four additional cases (three women) had no known phenotypic marker (unclassified HCA). The use of oral contraceptives was found only in two unclassified HCA (29%) cases. Fatty change of the background liver was seen in one β-catenin-activated HCA cases, four IHCA (57%) and two unclassified HCA (50%). Hepatic fibrosis was seen in five IHCA (71%) and two unclassified HCA (50%) cases. Four IHCA patients (one woman) were alcohol drinkers and one had alcoholic steatofibrosis and three had alcoholic cirrhosis. Eight HCA (57%) were multiple; one HNF1α-inactivated HCA (100%), four IHCA (57%) and three unclassified HCA (75%). The tumor was significantly larger in β-catenin-activated HCA than in other subgroups. The association of hepatocellular carcinoma was seen only in one case of unclassified HCA.

CONCLUSION

  This study suggests that IHCA arising in men with alcoholic liver disease may be a major subtype of HCA in Japan.

New monoallelic (partial tandem duplication) mutation of HNF1a gene in steatotic hepatocellular adenoma

Hepatocellular adenomas (HCAs) containing inactivating HNF1a mutations correspond to a homogenous group of tumors with marked steatosis and no cytological abnormalities or inflammatory infiltrates. We report a case of a 60-year-old woman who was referred with a 13-cm mass in the left lobe of the liver with no history of oral contraception use and no family history of note. Histology revealed a severely steatotic HCA. Immunohistochemistry showed no nuclear staining for β-catenin, limited glutamine synthetase positivity, and slightly attenuated liver-fatty acid binding protein staining. Serum amyloid A2 antibodies produced a coarse granular staining. Mutational screening detected monoallelic partial tandem duplication within exon 4 of TCF1 in tumoral tissue. No mutations in the β-catenin and IL6ST genes were detected. Quantitative reverse transcription PCR showed lower expression levels of FABP1 and uridine glycosyltransferase 2B7 and higher levels of serum amyloid A2 in tumor than in normal hepatocytes. Clinicopathological and molecular investigation of HCA cases with unique features could result in a better understanding of HCAs pathogenesis.

Validation of a liver adenoma classification system in a tertiary referral centre: implications for clinical practice

BACKGROUND & AIMS

A molecular and pathological classification system for hepatocellular adenomas (HCA) was recently introduced and four major subgroups were identified. We aimed to validate this adenoma classification system and to determine the clinical relevance of the subtypes for surgical management.

METHODS

Paraffin fixed liver tissue slides and resection specimens of patients radiologically diagnosed as HCA were retrieved from the department of pathology. Immunostainings included liver-fatty acid binding protein (L-FABP), serum amyloid A (SAA), C-reactive protein (CRP), glutamine synthetase (GS) and β-catenin.

RESULTS

From 2000 to 2010, 58 cases (71 lesions) were surgically resected. Fourteen lesions were diagnosed as focal nodular hyperplasia with a characteristic map-like staining pattern of GS. Inflammatory HCA expressing CRP and SAA was documented in 36 of 57 adenomas (63%). Three of these inflammatory adenomas were also β-catenin positive as well as GS positive and only one was CRP and SAA and GS positive. We identified eleven L-FABP-negative HCA (19%) and four β-catenin positive HCA (7%), without expression of CRP and SAA and with normal L-FABP staining, one of which was also GS positive. Six HCA were unclassifiable (11%). In three patients multiple adenomas of different subtypes were found.

CONCLUSIONS

Morphology and additional immunohistochemical markers can discriminate between different types of HCA in>90% of cases and this classification, including the identification of β-catenin positive adenomas may have important implications in the decision for surveillance or treatment. Interpretation of nuclear staining for β-catenin can be difficult due to uneven staining distribution or focal nuclear staining and additional molecular biology may be required.

Recent advances in cytogenetics and molecular biology of adult hepatocellular tumors: implications for imaging and management

Focal nodular hyperplasia (FNH), hepatocellular adenoma (HCA), and hepatocellular carcinoma (HCC) compose hepatocellular neoplasms that occur in adults. These tumors demonstrate characteristic epidemiologic and histopathologic features and clinical and imaging manifestations. HCAs are monoclonal neoplasms characterized by increased predilection to hemorrhage or rupture and occasional transformation to HCC. On the other hand, FNH is a polyclonal tumorlike lesion that occurs in response to increased perfusion and has an indolent clinical course. Up to 90% of HCCs occur in the setting of cirrhosis. Chronic viral hepatitis (hepatitis B and hepatitis C) infection and metabolic syndrome are major risk factors that can induce HCCs in nonfibrotic liver. Recent advances in pathology and genetics have led to better understanding of the histogenesis, natural history, and molecular events that determine specific oncologic pathways used by these neoplasms. HCAs are now believed to result from specific genetic mutations involving TCF1 (transcription factor 1 gene), IL6ST (interleukin 6 signal transducer gene), and CTNNB1 (β catenin-1 gene); FNHs are characterized by an "imbalance" of angiopoietin. While the β catenin signaling pathway is associated with well- and moderately differentiated HCCs, mutations involving p53 (tumor protein 53 gene), MMP14 (matrix metalloproteinase 14 gene), and RhoC (Ras homolog gene family, member C) are associated with larger tumor size, higher tumor grade with resultant shortened tumor-free survival, and poor prognosis. Fibrolamellar carcinoma (FLC), a unique HCC subtype, exhibits genomic homogeneity that partly explains its better overall prognosis. On the basis of recent study results involving cytogenetics and oncologic pathways of HCCs, novel drugs that act against molecular targets are being developed. Indeed, sorafenib (a multikinase inhibitor) is currently being used in the successful treatment of patients with advanced HCC. Characterization of genetic abnormalities and genotype-phenotype correlations in adult hepatocellular tumors provides better understanding of tumor pathology and biology, imaging findings, prognosis, and response to molecular therapeutics.

Pigmented hepatocellular adenoma: report of a case

Hepatocellular adenoma is a rare, benign neoplasm that is related to the use of contraceptives or androgenic-anabolic steroids. A 51-year-old man with no history of steroid use was found to have a liver tumor. Plain computed tomography showed a high-density tumor that was enhanced in the arterial phase, and the enhancement was prolonged in the delayed phase. Magnetic resonance imaging showed that the tumor was hyperintense on in- and opposed-phase T1-weighted gradient recalled echo images and hyperintense on T1-weighted spin echo images. A partial hepatic resection was performed. A histological examination revealed normal hepatocyte-like tumor cells, composed of abundant dark brown granules of Dubin-Johnson-like pigment, which stained positively for Masson-Fontana stain. The tumor was diagnosed to be a very rare hepatocellular adenoma with the deposition of Dubin-Johnson-like pigment.

Surgicopathological classification of hepatic space-occupying lesions: A single-center experience with literature review

Accompanying rapid developments in hepatic surgery, the number of surgeries and identifications of histological types of primary hepatic space-occupying lesions (PHSOLs) have increased dramatically. This has led to many changes in the surgicopathological spectrum of PHSOLs, and has contributed to a theoretical basis for modern hepatic surgery and oncological pathology. Between 1982 and 2009 at the Eastern Hepatobiliary Surgery Hospital (EHBH) in Shanghai, 31 901 patients underwent surgery and were diagnosed as having a PHSOL. In this paper, we present an analysis of the PHSOL cases at the EHBH for this time period, along with results from a systematic literature review. We describe a surgicopathological spectrum comprising more than 100 types of PHSOLs that can be stratified into three types: tumor-like, benign, and malignant. We also stratified the PHSOLs into six subtypes derived from hepatocytes; cholangiocytes; vascular, lymphoid and hemopoietic tissues; muscular, fibrous and adipose tissues; neural and neuroendocrine tissues; and miscellaneous tissues. The present study provides a new classification system that can be used as a current reference for clinicians and pathologists to make correct diagnoses and differential diagnoses among various PHSOLs.

Molecular pathology of hepatic neoplasms: classification and clinical significance

Recent technological advances have enabled investigators to characterize the molecular genetics and genomics of hepatic neoplasia in remarkable detail. From these studies, an increasing number of molecular markers are being identified that correlate with clinically important tumor phenotypes. This paper discusses current knowledge relevant to the molecular classification of epithelial primary hepatic tumors that arise in adults, including focal nodular hyperplasia (FNH), hepatocellular adenoma (HCA), hepatocellular carcinoma (HCC), cholangiocarcinoma (CC), and combined HCC-CC. Genetic analysis has defined molecular subtypes of HCA that are clinicopathologically distinct and can be distinguished through immunohistochemistry. Gene expression studies have identified molecular signatures of progression from dysplastic nodules (DNs) to early HCC in cirrhosis. Analyses of the mutational spectra, chromosomal aberrations and instability, transcriptomics, and microRNA profiles of HCC have revealed the existence of biologically distinct subtypes of this common malignancy, with prognostic implications. Molecular characterization of biliary and hepatic progenitor cell phenotypes in liver cancer has shed new light on the histogenesis of these tumors and has focused attention on novel therapeutic targets. In coming years, the molecular classification of hepatic neoplasms will be increasingly valuable for guiding patient care, as targeted therapies for liver cancer are developed and brought into clinical practice.

Hepatocellular adenomas: accuracy of magnetic resonance imaging and liver biopsy in subtype classification

Hepatocellular adenomas (HCAs) are divided into genotype/phenotype subgroups associated with different evolutive profiles. Therefore, recognition of subtype is of clinical importance in patient management. Magnetic resonance imaging (MRI) is considered the most informative imaging modality and liver biopsy a key diagnostic tool whose role in HCA subtyping has never been extensively studied. The purpose of our study was to evaluate the diagnostic performance of MRI and liver biopsy with and without immunohistochemistry and to assess the interobserver agreement for MR classification in a consecutive series of resected HCAs. Forty-seven HCAs with preoperative MRI and biopsy were retrospectively included. MRI data were reviewed independently by two abdominal radiologists blind to the pathological results and classification. Subtyping of HCAs on liver biopsy was made blindly to clinical, biological, and imaging data and to final classification. Routine histological analysis was based on morphological criteria and immunohistochemistry was systematically performed when enough tissue was available. Final subtyping of HCA was based on the examination of the surgical specimen. Radiologists correctly classified HCAs in 85%. The interobserver kappa correlation coefficient was 0.86. Routine histological analysis led to 76.6% of correct classification and 81.6% when immunophenotypical characteristics were available. The additional value of immunophenotypical markers is best in HCAs containing steatosis. Agreement between MRI findings and routine histological analysis was observed in 74.5%, leading to a likelihood ratio of subtype diagnosis higher than 20.

CONCLUSION

MRI and biopsy analysis are two efficient methods in subtyping HCAs and their association increases the diagnosis confidence. Interobserver variability in MRI criteria is very low.

Focal nodular hyperplasia with major sinusoidal dilatation: a misleading entity

Focal nodular hyperplasia (FNH) is a benign liver lesion thought to be a non-specific response to locally increased blood flow. Although the diagnosis of FNH and hepatocellular adenoma (HCA) has made great progress over the last few years using modern imaging techniques, there are still in daily practice some difficulties concerning some atypical nodules. Here, the authors report the case of a 47-year-old woman with a single liver lesion thought to be, by imaging, an inflammatory HCA with major sinusoidal congestion. This nodule was revealed to be, at the microscopical level and after specific immunostaining and molecular analysis, an FNH with sinusoidal dilatation (so-called telangiectatic focal nodular hyperplasia).

Focal nodular hyperplasia of the liver: an unusual association with diabetes mellitus in a child and review of literature

Hepatic hemangioma, adenoma and focal nodular hyperplasia are the most frequent benign lesions of the liver, but they are all infrequent among pediatric population. The reports of focal nodular hyperplasia in children have recently increased in number, with many cases associated to drug intake, particularly to chemotherapy. We here describe, to our knowledge, the first case of focal nodular hyperplasia in association with diabetes mellitus in childhood.

Clonality and allelotype analyses of focal nodular hyperplasia compared with hepatocellular adenoma and carcinoma

AIM: To identify clonality and genetic alterations in focal nodular hyperplasia (FNH) and the nodules derived from it.

METHODS: Twelve FNH lesions were examined. Twelve hepatocellular adenomas (HCAs) and 22 hepatocellular carcinomas (HCCs) were used as references. Nodules of different types were identified and isolated from FNH by microdissection. An X-chromosome inactivation assay was employed to describe their clonality status. Loss of heterozygosity (LOH) was detected, using 57 markers, for genetic alterations.

RESULTS: Nodules of altered hepatocytes (NAH), the putative precursors of HCA and HCC, were found in all the FNH lesions. Polyclonality was revealed in 10 FNH lesions from female patients, and LOH was not detected in any of the six FNH lesions examined, the results apparently showing their polyclonal nature. In contrast, monoclonality was demonstrated in all the eight HCAs and in four of the HCCs from females, and allelic imbalances were found in the HCAs (9/9) and HCCs (15/18), with chromosomal arms 11p, 13q and 17p affected in the former, and 6q, 8p, 11p, 16q and 17p affected in the latter lesions in high frequencies (≥ 30%). Monoclonality was revealed in 21 (40%) of the 52 microdissected NAH, but was not found in any of the five ordinary nodules. LOH was found in all of the 13 NAH tested, being highly frequent at six loci on 8p, 11p, 13q and 17p.

CONCLUSION: FNH, as a whole, is polyclonal, but some of the NAH lesions derived from it are already neoplastic and harbor similar allelic imbalances as HCAs.

C-11 acetate does not enhance usefulness of F-18 FDG PET/CT in differentiating between focal nodular hyperplasia and hepatic adenoma

PURPOSE OF THE REPORT

We assessed the usefulness of F-18 fluorodeoxyglucose positron emission tomography (FDG PET) and C-11 acetate PET (AC PET) in distinguishing hepatic lesions due to consequential disease (hepatocellular adenoma and malignant lesions) from focal nodular hyperplasia (FNH) in patients at low risk of malignancy.

MATERIALS AND METHODS

Thirty-one patients with 43 lesions were prospectively enrolled. The diagnostic work-up included Doppler and contrast-enhanced ultrasonography, contrast-enhanced computed tomography, and/or magnetic resonance imaging. Fine needle biopsy was performed if the imaging study was inconclusive. The work-up revealed 36 FNH and 7 consequential lesions (5 hepatocellular adenoma, 1 hepatoma, and 1 metastasis). All patients underwent FDG and AC PET. FDG PET with target/background ratio (T/Br) greater than 1.2 and AC PET with T/Br of less than 1.2 were considered positive test for consequential disease.

RESULTS

On FDG PET, we had 6 true-positive out of 7 lesions due to consequential diseases, with a sensitivity of 85.7%, and 33 true-negative out of 36 lesions with FNH, with a specificity of 91.7%. Using AC PET, there were 2 true-positive lesions out of 7 caused by neoplasms, with a sensitivity of 28.6%, and 34 true-negative lesions out of 36 FNH, with a specificity of 94.4%.

CONCLUSIONS

When the goal is differentiating FNH from liver neoplasms, AC PET offered no additional diagnostic advantage over what is achieved with FDG PET.

[Incidental ultrasound finding of a 3 cm liver nodule in a 45-year-old woman taking hormonal substitution after hysterectomy performed for cervix carcinoma]

Incidental liver nodules are more and more frequently encountered because of increasing sensitivity of recent imaging techniques. The identification of biliary cyst or hemangioma is usually easy. In other cases, the etiological diagnosis relies on careful radiological analysis of the pattern of the arterial phase enhancement following contrast medium injection. When there is no early arterial enhancement, a liver biopsy is usually indicated to establish the diagnosis. A strong arterial contrast enhancement pattern is indicative of hepatocellular tumor, benign or malignant. In this situation, it is crucial to establish if there is underlying liver fibrosis. In case of cirrhosis, the diagnosis of hepatocellular carcinoma is the most probable. If the non tumorous liver is normal, focal nodular hyperplasia and hepatocellular adenoma should be differentiated. The distinction between these two tumors is important because only hepatic adenoma carries a significant risk of complications (bleeding or hepatocellular carcinoma) leading to surgical resection of lesions that do not regress after steroid withdrawal. Contrast enhanced MRI and contrast ultrasound are most useful tools for the diagnosis of nodular regenerative hyperplasia but liver biopsy can be necessary in atypical forms. In recent years, the understanding of molecular mechanisms associated with adenoma occurrence allowed for the proposal of a new classification already of practical interest in the management of patients.

Role of Wnt/β-catenin signaling in liver metabolism and cancer

Wnt/β-catenin signaling is known for its role in embryogenesis as well as carcinogenesis. In the liver, it plays many critical roles during hepatic development and regeneration, and its dysregulation is evident in aberrant hepatic growth during various liver tumors. Its chief cellular roles in the liver include regulation of processes of cell proliferation, apoptosis, oxidative stress and differentiation, which in turn contributes to hepatic growth, zonation, xenobiotic metabolism and other metabolic processes inherent to the liver. Most of these functions of the Wnt/β-catenin signaling are dictated through the highly temporal and tissue-specific or non-specific transcriptional targets of the pathway. In addition, some of the critical functions such as cell-cell adhesion and perhaps maintenance of various junctions that are critical from an epithelial cell biology perspective are also a function of β-catenin, which is the central component of the canonical Wnt pathway. Various animal models and clinical studies have demonstrated the spectra of Wnt/β-catenin signaling in liver health and disease. Thus therapeutic modulation of this pathway for improved hepatic health is inevitable in the future. The current review discusses the advances in our understanding of the Wnt/β-catenin signaling in liver physiology and pathology especially in hepatic metabolism and various tumors in adult liver and goes on to extrapolate the pre-clinical significance and possible translational implications of such findings.

Role of Wnt/β-catenin signaling in liver metabolism and cancer

Wnt/β-catenin signaling is known for its role in embryogenesis as well as carcinogenesis. In the liver, it plays many critical roles during hepatic development and regeneration, and its dysregulation is evident in aberrant hepatic growth during various liver tumors. Its chief cellular roles in the liver include regulation of processes of cell proliferation, apoptosis, oxidative stress and differentiation, which in turn contributes to hepatic growth, zonation, xenobiotic metabolism and other metabolic processes inherent to the liver. Most of these functions of the Wnt/β-catenin signaling are dictated through the highly temporal and tissue-specific or non-specific transcriptional targets of the pathway. In addition, some of the critical functions such as cell-cell adhesion and perhaps maintenance of various junctions that are critical from an epithelial cell biology perspective are also a function of β-catenin, which is the central component of the canonical Wnt pathway. Various animal models and clinical studies have demonstrated the spectra of Wnt/β-catenin signaling in liver health and disease. Thus therapeutic modulation of this pathway for improved hepatic health is inevitable in the future. The current review discusses the advances in our understanding of the Wnt/β-catenin signaling in liver physiology and pathology especially in hepatic metabolism and various tumors in adult liver and goes on to extrapolate the pre-clinical significance and possible translational implications of such findings.

Hepatocellular adenoma management and phenotypic classification: the Bordeaux experience

We took advantage of the reported genotype/phenotype classification to analyze our surgical series of hepatocellular adenoma (HCA). The series without specific known etiologies included 128 cases (116 women). The number of nodules varies from single, <5, and >or=5 in 78, 38, and 12 cases, respectively. The resection was complete in 95 cases. We identified 46 HNF1alpha-inactivated HCAs (44 women), 63 inflammatory HCAs (IHCA, 53 women) of which nine were also beta-catenin-activated, and seven beta-catenin-activated HCAs (all women); six additional cases had no known phenotypic marker and six others could not be phenotypically analyzed. Twenty-three of 128 HCAs showed bleeding. No differences were observed in solitary or multiple tumors in terms of hemorrhagic manifestations between groups. In contrast, differences were observed between the two main groups. Steatosis (tumor), microadenomas (resected specimen), and additional benign nodules were more frequently observed in HNF1alpha-inactivated HCAs (P < 0.01) than in IHCAs. Body mass index > 25, peliosis (tumor), and steatosis in background liver were more frequent in IHCA (P < 0.01). After complete resection, new HCAs in the centimetric range were more frequently found during follow-up (>1 year) in HNF1alpha-inactivated HCA. After incomplete resection (HCA left in nonresected liver), the majority of HCA remained stable in the two main groups and even sometimes regressed. Six patients of 128 developed hepatocellular carcinoma (HCC) (all were beta-catenin-activated, whether inflammatory or not).

CONCLUSION

There were noticeable clinical differences between HNF1alpha-inactivated HCA and IHCA; there was no increased risk of bleeding or HCC related to the number of HCAs; beta-catenin-activated HCAs are at higher risk of HCC. As a consequence, we believe that management of HCA needs to be adapted to the phenotype of these tumors.

Agrin and CD34 immunohistochemistry for the discrimination of benign versus malignant hepatocellular lesions

Agrin is a recently identified proteoglycan component of vascular and bile duct basement membranes in the liver. The selective deposition of agrin in hepatocellular carcinoma (HCC) microvessels versus sinusoidal walls prompted us to investigate the utility of agrin immunohistochemistry (IHC) in detecting malignant hepatocellular lesions. We focused on the differential diagnostic problems often presented by hepatocellular adenomas (HCAs) and dysplastic nodules. IHC for agrin was performed on 138 formalin-fixed, paraffin-embedded surgical specimens from 93 patients, including cirrhotic liver tissues (25), focal nodular hyperplasia (10), large regenerative nodules (8), low-grade (23) and high-grade (7) dysplastic nodules, small HCC (8), HCC (27), and HCA (30). Agrin immunostaining was compared with that of CD34 and, in selected cases, to glypican-3. The combination of agrin and CD34 sensitively (0.94) and specifically (0.93) identified lesions judged previously as malignant by histology. The majority of benign lesions were clearly agrin-negative, whereas the strength and extent of agrin IHC faithfully reflected dysplasia in "atypical" HCAs and in high-grade dysplastic nodules. Malignant lesions were uniformly positive. In conclusion, as agrin is highly selective for tumor blood vessels, IHC for agrin facilitates the discrimination of benign and malignant hepatocellular lesions. Moreover, whereas glypican-3 in some HCCs may appear in few scattered cells only, agrin is diffusely deposited in virtually all malignant lesions, which may prove advantageous in the evaluation of small specimens such as core biopsies.

Approach to a liver mass

Incidentally discovered liver masses are becoming more common with the increasing application and power of imaging techniques for the evaluation of abdominal conditions. Although such masses are often benign, conclusive diagnoses must be established in order to provide appropriate patient care. Various imaging modalities can be utilized to accurately diagnose such masses without resort to more invasive diagnostic measures.

MicroRNA involvement in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the third cause of cancer-related death worldwide. Curative options for HCC are limited and exclusively available for patients carrying an early stage HCC. In advanced stages, traditional chemotherapy proved to be only marginally effective or even toxic. Thus, the identification of new treatment options is needed. New targets for non-conventional treatment will necessarily take advantage of progresses on the molecular pathogenesis of HCC. MicroRNAs (miRNAs) are a group of tiny RNAs with a fundamental role in the regulation of gene expression. Aberrant expression of several miRNAs was found to be involved in human hepatocarcinogenesis. miRNA expression signatures were correlated with bio-pathological and clinical features of HCC. In some cases, aberrantly expressed miRNAs could be linked to cancer-associated pathways, indicating a direct role in liver tumourigenesis. For example, up-regulation of mir-221 and mir-21 could promote cell cycle progression, reduce cell death and favour angiogenesis and invasion. These findings suggest that miRNAs could become novel molecular targets for HCC treatment. The demonstration of in vivo efficacy and safety of anti-miRNA compounds has opened the way to their use in clinical trials.

Interaction of major genes predisposing to hepatocellular carcinoma with genes encoding signal transduction pathways influences tumor phenotype and prognosis

Studies on rodents and humans demonstrate an inherited predisposition to hepatocellular carcinoma (HCC). Analysis of the molecular alterations involved in the acquisition of a phenotype resistant or susceptible to hepatocarcinogenesis showed a deregulation of G1 and S phases in HCC of genetically susceptible F344 rats and a G1-S block in lesions of resistant Brown norway (BN) rats. Unrestrained extracellular signal-regulated kinase (ERK) activity linked to proteasomal degradation of dual-specificity phosphatase 1 (DUSP1), a specific ERK inhibitor, by the CKS1-SKP2 ubiquitin ligase complex occurs in more aggressive HCC of F344 rats and humans. This mechanism is less active in HCC of BN rats and human HCC with better prognosis. Upregulation of iNos cross-talk with IKK/NF-κB and RAS/ERK pathways occurs in rodent liver lesions at higher levels in the most aggressive models represented by HCC of F344 rats and c-Myc-TGF-α transgenic mice. iNOS, IKK/NF-κB, and RAS/ERK upregulation is highest in human HCC with a poorer prognosis and positively correlates with tumor proliferation, genomic instability and microvascularization, and negatively with apoptosis. Thus, cell cycle regulation and the activity of signal transduction pathways seem to be modulated by HCC modifier genes, and differences in their efficiency influence the susceptibility to hepatocarcinogenesis and probably the prognosis of human HCC.

Wnt signaling in liver cancer

Hepatocellular carcinoma (HCC) is a major cause of cancer death worldwide. As in many other types of cancer, aberrant activation of the canonical Wnt/beta-catenin signaling pathway is an important contributor to tumorigenesis. In HCC this frequently occurs through mutations in the N-terminal region of beta-catenin that stabilize the protein and permit an elevated level of constitutive transcriptional activation by beta-catenin/TCF complexes. In this article we review the abundant evidence that Wnt/beta-catenin signaling contributes to liver carcinogenesis. We also discuss what is known about the roles of Wnt signaling in liver development, regeneration, and stem cell behavior, in an effort to understand the mechanisms by which activation of the canonical Wnt pathway promotes tumor formation in this organ. The Wnt/beta-catenin pathway presents itself as an attractive target for developing novel rational therapies for HCC, a disease for which few successful treatment strategies are currently available.

Hepatocellular adenomas: magnetic resonance imaging features as a function of molecular pathological classification

Hepatocellular adenomas (HCAs) are a group of benign tumors forming three molecular pathological subgroups: (1) hepatocyte nuclear factor 1alpha (HNF-1alpha)-inactivated, (2) beta-catenin-activated, and (3) inflammatory. Some HCAs present both beta-catenin activation and inflammation. We analyzed magnetic resonance imaging (MRI) data for correlations between features on imaging and pathological classification of HCAs. We included 50 cases for which pathology specimens were classified into three groups based on immunohistochemical staining. Two characteristic MRI profiles were identified corresponding to HNF-1alpha-inactivated and inflammatory HCAs. Fifteen HCAs were HNF-1alpha-inactivated. The corresponding lesions showed (1) diffuse signal dropout on T1-weighted chemical shift sequence due to steatosis, (2) isosignal or slight hypersignal on T2-weighted (T2W) images, and (3) moderate enhancement in the arterial phase, with no persistent enhancement in the portal venous and delayed phases. For the diagnosis of HNF-1alpha-inactivated HCA, the positive predictive value of homogeneous signal dropout on chemical shift images was 100%, the negative predictive value was 94.7%, the sensitivity was 86.7%, and the specificity was 100%. Twenty-three HCAs were inflammatory and showed (1) an absence or only focal signal dropout on chemical shift sequence; (2) marked hypersignal on T2W sequences, with a stronger signal in the outer part of the lesions, correlating with sinusoidal dilatation areas; and (3) strong arterial enhancement, with persistent enhancement in the portal venous and delayed phases. Marked hypersignal on T2W sequences associated with delayed persistent enhancement had a positive predictive value of 88.5%, a negative predictive value of 84%, a sensitivity of 85.2%, and a specificity of 87.5% for the diagnosis of inflammatory HCA.

CONCLUSION

HNF-1alpha-mutated HCAs and inflammatory HCAs were associated with specific MRI patterns related to diffuse fat repartition and sinusoidal dilatation, respectively.

Unexpected discovery of 2 cases of hepatocyte nuclear factor 1α-mutated infracentimetric adenomatosis

We present 2 cases of hepatocyte nuclear factor 1α (HNF1α)-mutated adenomatosis, discovered for reasons unrelated to this disease, and identified using immunohistochemical methods. These new tools may further our understanding of the link between adenomas/adenomatosis subtypes and their complications, and their association with other abnormalities.

Surgical management of hepatocellular adenoma: take it or leave it?

BACKGROUND

Hepatocellular adenoma (HA) is a rare benign tumor of the liver. Surgical resection is generally indicated to reduce risks of hemorrhage and malignant transformation. We sought to evaluate clinical presentation, surgical management, and outcomes of patients with HA at our institution.

METHODS

We performed a retrospective review of 41 patients who underwent surgical resection for HA between 1988 and 2007.

RESULTS

Thirty-eight patients were women, and the median age at presentation was 36 years (range, 19-65 years). The most common clinical presentation was abdominal pain (70%) followed by incidental radiological finding (17%). Twenty-two patients had a history of oral contraceptive use. Median number of HA was one (range, 1-3). There were 32 open cases (3 trisectionectomy, 15 hemihepatectomy, 7 sectionectomy, 4 segmentectomy, and 3 wedge resection), and 9 laparoscopic cases (1 hemihepatectomy, 5 sectionectomy, 1 segmentectomy, and 2 wedge resection). The median estimated blood loss was 225 mL (range, 0-3400 mL). The median length of stay was 6 days (range, 1-15 days). Surgical morbidities included pleural effusion requiring percutaneous drainage (n = 2), pneumonia (n = 1), and wound infection (n = 1). There was no perioperative mortality. Twelve patients had hemorrhage from HA. Hepatocellular carcinoma was observed in two patients with HA. Median follow-up was 23 months (range, 1-194 months), at which time all patients were alive.

CONCLUSION

In view of 29% hemorrhagic and 5% malignant complication rates, we recommend surgical resection over observation if patient comorbidities and anatomic location of HA are favorable. A laparoscopic approach can be safely used in selected cases.

The beta-catenin pathway is activated in focal nodular hyperplasia but not in cirrhotic FNH-like nodules

BACKGROUND/AIMS

Focal nodular hyperplasias (FNHs) are benign liver lesions considered to be a hyperplastic response to increased blood flow in normal liver. In contrast, FNH-like lesions/nodules occur in cirrhotic liver but share similar histopathological features. We conducted a transcriptome analysis to identify biological pathways deregulated in FNH.

METHODS

Gene expression profiles obtained in FNH and normal livers were compared. Differentially-expressed genes were validated using quantitative-RT-PCR in 70 benign liver tumors including FNH-like lesions.

RESULTS

Among the deregulated genes in FNHs, 19 displayed physiological restricted distribution in the normal liver. All six perivenous genes were up-regulated in FNH, whereas 13 periportal genes were down-regulated. Almost all these genes are known to be regulated by beta-catenin. Glutamine synthetase was markedly overexpressed in anastomosed areas usually centered on visible veins. Moreover, activated hypophosphorylated beta-catenin protein accumulated in FNH in the absence of activating mutations. These results suggest the zonated activation of the beta-catenin pathway in FNH, whereas the other benign hepatocellular tumors, including FNH-like lesions, demonstrated an entirely different pattern of beta-catenin expression.

CONCLUSIONS

In FNH, increased activation of the beta-catenin pathway was found restricted to enlarged perivenous areas. FNH-like nodules may have a different pathogenetic origin.

Management and surgical treatment for focal nodular hyperplasia in children

Focal nodular hyperplasia (FNH) is rare in pediatric liver tumor. To investigate the experience in the appropriate management of pediatric FNH, the records of consecutive children who were managed at our institute from 2000 to 2007were reviewed for FNH. There were four males and nine females whose ages ranged from 26 months to 18 years with a mean of 11.7 years. FNH in most children was detected by medical examination for abdominal pain (61.5%) or other symptoms. All the 13 pediatric patients underwent liver resection. There was no operative death or postoperative complications. The children were regularly followed up ranging from 2 to 85 months and they were healthy without recurrence. For pediatric FNH patients with clinical symptoms or indefinite diagnosis, it is suggested that active surgical treatment by hepatectomy should be performed.

MicroRNA profiling in hepatocellular tumors is associated with clinical features and oncogene/tumor suppressor gene mutations

Molecular classifications defining new tumor subtypes have been recently refined with genetic and transcriptomic analyses of benign and malignant hepatocellular tumors. Here, we performed microRNA (miRNA) profiling in two series of fully annotated liver tumors to uncover associations between oncogene/tumor suppressor mutations and clinical and pathological features. Expression levels of 250 miRNAs in 46 benign and malignant hepatocellular tumors were compared to those of 4 normal liver samples with quantitative reverse-transcriptase polymerase chain reaction. miRNAs associated with genetic and clinical characteristics were validated in a second series of 43 liver tumor samples and 16 nontumor samples. miRNA profiling unsupervised analysis classified samples in unique clusters characterized by histological features (tumor/nontumor, P < 0.001; benign/malignant tumors, P < 0.01; inflammatory adenoma and focal nodular hyperplasia, P < 0.01), clinical characteristics [hepatitis B virus (HBV) infection, P < 0.001; alcohol consumption, P < 0.05], and oncogene/tumor suppressor gene mutations [beta-catenin, P < 0.01; hepatocyte nuclear factor 1alpha (HNF1alpha), P < 0.01]. Our study identified and validated miR-224 overexpression in all tumors and miR-200c, miR-200, miR-21, miR-224, miR-10b, and miR-222 specific deregulation in benign or malignant tumors. Moreover, miR-96 was overexpressed in HBV tumors, and miR-126* was down-regulated in alcohol-related hepatocellular carcinoma. Down-regulations of miR-107 and miR-375 were specifically associated with HNF1alpha and beta-catenin gene mutations, respectively. miR-375 expression was highly correlated to that of beta-catenin-targeted genes as miR-107 expression was correlated to that of HNF1alpha in a small interfering RNA cell line model. Thus, this strongly suggests that beta-catenin and HNF1alpha could regulate miR-375 and miR-107 expression levels, respectively.

CONCLUSION

Hepatocellular tumors may have a distinct miRNA expression fingerprint according to malignancy, risk factors, and oncogene/tumor suppressor gene alterations. Dissecting these relationships provides a new hypothesis to understand the functional impact of miRNA deregulation in liver tumorigenesis and the promising use of miRNAs as diagnostic markers.

Hepatocellular adenoma: what is new in 2008

Patients (85%) with hepatocellular adenoma (HCA) are women taking oral contraceptives. They can be divided into four subgroups according to their genotype/phenotype features. (1) Hepatocyte nuclear factor 1α (HNF1α) biallelic somatic mutations are observed in 35% of the HCA cases. It occurs in almost all cases in women. HNF1α-mutated HCA are most of the time, highly steatotic, with a lack of expression of liver fatty acid binding protein (LFABP) in immunohistochemistry analyses. Adenomatosis is frequently detected in this context. An HNF1α germline mutation is observed in less than 5% of HCA cases and can be associated with MODY 3 diabetes. (2) An activating β-catenin mutation was found in 10% of HCA. These β-catenin activated HCAs are observed in men and women, and specific risk factors, such as male hormone administration or glycogenosis, are associated with their development. Immunohistochemistry studies show that these HCAs overexpress β-catenin (nuclear and cytoplasmic) and glutamine synthetase. This group of tumours has a higher risk of malignant transformation into hepatocellular carcinoma. (3) Inflammatory HCAs are observed in 40% of the cases, and they are most frequent in women but are also found in men. Lesions are characterised by inflammatory infiltrates, dystrophic arteries, sinusoidal dilatation and ductular reaction. They express serum amyloid A and C-reactive protein. In this group, GGT is frequently elevated, with a biological inflammatory syndrome present. Also, there are more overweight patients in this group. An additional 10% of inflammatory HCAs express β-catenin, and are also at risk of malignant transformation. (4) Currently, less than 10% of HCAs are unclassified. It is hoped that in the near future it will be possible with clinical, biological and imaging data to predict in which of the 2 major groups (HNF1α-mutated HCA and inflammatory HCA) the patient belongs and to propose better guidelines in terms of surveillance and treatment.