Pathological diagnosis of liver cell adenoma and focal nodular hyperplasia: Bordeaux update

Clinicopathological analysis of hepatocellular adenoma according to new bordeaux classification: report of eight korean cases

Background

Hepatocellular adenoma (HCA) is a rare benign tumor of the liver. A subtype classification of HCA (hepatocyte nuclear factor 1α [HNF1α]-mutated, β-catenin-mutated HCA, inflammatory HCA, and unclassified HCA) has recently been established based on a single institutional review of a HCA series by the Bordeaux group.

Methods

We used histologic and immunohistochemical parameters to classify and evaluate eight cases from our institution. We evaluated the new classification method and analyzed correlations between our results and those of other reports.

Results

Seven of our eight cases showed histologic and immunohistochemical results consistent with previous reports. However, one case showed overlapping histologic features, as previously described by the Bordeaux group. Four cases showed glutamine synthetase immunohistochemical staining inconsistent with their classification, indicating that glutamine synthetase staining may not be diagnostic for β-catenin-mutated HCA. HNF1α-mutated HCA may be indicated by the absence of liver fatty acid binding protein expression. Detection of amyloid A may indicate inflammatory HCA. HCA with no mutation in the HNF1α or β-catenin genes and no inflammatory protein expression is categorized as unclassified HCA.

Conclusions

Although the new classification is now generally accepted, validation through follow-up studies is necessary.

Diagnostic Approach to Hepatic Mass Lesions and Role of Immunohistochemistry

This review provides an overview of various hepatic mass lesions and a practical diagnostic approach, including most recent immunohistochemical stains used in clinical practice. A wide variety of benign and malignant lesions present as hepatic masses, and the differential diagnosis varies. In cirrhotic liver, the commonest malignant tumor is hepatocellular carcinoma (HCC), which needs to be differentiated from macroregenerative nodules, dysplastic nodules, and other tumors. The differential diagnosis of lesions in noncirrhotic liver in younger patients includes hepatic adenoma (HA), focal nodular hyperplasia (FNH), HCC, and other primary hepatic neoplasms and metastases. In older populations, metastases remain the most common mass lesions.

Focal Nodular Hyperplasia and Hepatocellular Adenoma around the World Viewed through the Scope of the Immunopathological Classification

Focal nodular hyperplasia (FNH) and hepatocellular adenoma (HCA) are benign hepatocellular tumors. The risk of bleeding and malignant transformation of HCA are strong arguments to differentiate HCA from FNH. Despite great progress that has been made in the differential radiological diagnosis of the 2 types of nodules, liver biopsy is sometimes necessary to separate the 2 entities. Identification of HCA subtypes using immunohistochemical techniques, namely, HNF1A-inactivated HCA (35-40%), inflammatory HCA (IHCA), and beta-catenin-mutated inflammatory HCA (b-IHCA) (50-55%), beta-catenin-activated HCA (5-10%), and unclassified HCA (10%) has greatly improved the diagnostic accuracy of benign hepatocellular nodules. If HCA malignant transformation occurs in all HCA subgroups, the risk is by far the highest in the β -catenin-mutated subgroups (b-HCA, b-IHCA). In the coming decade the management of HCA will be more dependent on the identification of HCA subtypes, particularly for smaller nodules (<5 cm) in terms of imaging, follow-up, and resection.

Benign hepatocellular tumors in children: focal nodular hyperplasia and hepatocellular adenoma

Benign liver tumors are very rare in children. Most focal nodular hyperplasia (FNH) remain sporadic, but predisposing factors exist, as follows: long-term cancer survivor (with an increasing incidence), portal deprivation in congenital or surgical portosystemic shunt. The aspect is atypical on imaging in two-thirds of cases. Biopsy of the tumor and the nontumoral liver is then required. Surgical resection will be discussed in the case of large tumors with or without symptoms. In the case of associated vascular disorder with portal deprivation, restoration of the portal flow will be discussed in the hope of seeing the involution of FNH. HepatoCellular Adenoma (HCA) is frequently associated with predisposing factors such as GSD type I and III, Fanconi anemia especially if androgen therapy is administered, CPSS, and SPSS. Adenomatosis has been reported in germline mutation of HNF1- α . Management will depend on the presence of a predisposing factor and may include metabolic control, androgen therapy withdrawn, or closure of the shunt when appropriate. Surgery is usually performed on large lesions. In the case of adenomatosis or multiple lesions, surgery will be adapted. Close followup is required in all cases.

Molecular pathogenesis of hepatic adenomas and its implications for surgical management

INTRODUCTION

Hepatic adenomas (HAs) are benign tumors of the liver, which can be solitary or multiple, and have a definite risk of malignant degeneration.

DISCUSSION

The pathogenesis and natural history of this disease entity were previously unknown. Recent research into the molecular pathogenesis of this condition has provided evidence for the malignant transformation of some of these adenomas. In the current article, we discuss the current evidence on the molecular biology underlying malignant transformation of hepatic adenomas and the implications for the surgical management of this disease.

Laparoscopic partial hepatectomy of focal nodular hyperplasia

Focal nodular hyperplasia is a benign liver lesion incidentally discovered with increasing frequency because of the proliferation of imaging studies. Radiographic characterization can diagnose this pathologic lesion and nonoperative therapy is the standard of care. However, surgical resection may be required for diagnostic reasons or symptomatic patients. Depending on the anatomic location of the lesion, biopsy and/or resection can be performed laparoscopically. We herein report the case of a 26-year-old Japanese woman with a hepatic tumor who required a medical examination. Her medical history was negative for alcohol abuse, oral contraceptive administration and trauma. Clinical examination showed no significant symptoms. Ultrasonography, computed tomography and magnetic resonance imaging showed a mass located in the left lateral segment of the liver with a diameter of about 40 mm. It was difficult to diagnose the tumor definitively from these imaging studies, so we performed laparoscopic partial hepatectomy with successive firing of endoscopic staplers. The histopathological diagnosis was focal nodular hyperplasia. Surgical procedures and postoperative course were uneventful and the patient was discharged from the hospital on postoperative day 5.

MR findings of steatotic focal nodular hyperplasia and comparison with other fatty tumours

OBJECTIVES

To correlate MR findings with pathology in steatotic FNHs and to compare the MR findings with those of other fatty tumours developed on noncirrhotic liver in a consecutive series of resected lesions.

METHODS

Our population included resected FNH with intralesional steatosis (n = 25) and other resected fatty tumours selected as controls (hepatocellular adenomas and angiomyolipomas, n = 34). Lesions were classified into three groups: those with typical FNH without (group 1) or with (group 2) fat on MR and those with atypical lesions (group 3). In group 3, diagnostic criteria for other fatty tumours were applied.

RESULTS

There were 9 lesions in group 1 (15.3 %), 4 in group 2 (16.8 %) and 46 in group 3 (77.9 %). Group 3 contained 12 FNHs (26 %) and all the other fatty tumours. In group 3, the association of lesion homogeneity, signal intensity similar to or slightly different from adjacent liver on in-phase T1- and T2-weighted sequences, and strong arterial enhancement was observed in 7/12 (58 %) of steatotic FNHs and 3/34 (9 %) of other tumours.

CONCLUSION

On MR, fat within a typical FNH should not reduce the diagnostic confidence. We recommend further investigations including liver biopsy if necessary when fatty tumours exhibit atypical MR findings.

Diagnostic accuracy of MRI in differentiating hepatocellular adenoma from focal nodular hyperplasia: prospective study of the additional value of gadoxetate disodium

OBJECTIVE

The purpose of this article is to prospectively determine the sensitivity of hepatobiliary phase gadoxetate disodium-enhanced MRI combined with standard MRI in differentiating focal nodular hyperplasia (FNH) from hepatocellular adenoma (HCA).

SUBJECTS AND METHODS

Patients suspected of having FNH or HCA larger than 2 cm underwent gadoxetate disodium-enhanced MRI. Standard MRI was evaluated separately from the additional hepatobiliary phase by two blinded radiologists. For the largest lesion in each patient, findings were compared with histologic diagnosis. Sensitivity, positive predictive value (PPV), and distinctive features were analyzed using McNemar and analysis of variance tests.

RESULTS

Fifty-two patients completed the study. Histologic diagnosis revealed 24 HCAs and 28 FNHs. Characterization on standard MRI was inconclusive in 40% (21/52) and conclusive in 60% (31/52) of lesions. The sensitivity of standard MRI for HCA was 50% (12/24) with a PPV of 100% (12/12). The sensitivity for FNH was 68% (19/28) with a PPV of 95% (18/19). After review of hepatobiliary phase, the sensitivity for HCA improved to 96% (23/24) with a PPV of 96% (23/24). The sensitivity for FNH improved to 96% (27/28) with a PPV of 96% (27/28). Features with significant predictive value for diagnosis in HCA included bleeding (p < 0.001), fat (p = 0.010), and glycogen (p = 0.024). The presence of a central scar was predictive for FNH (p < 0.001).

CONCLUSION

This study shows high sensitivity of gadoxetate disodium-enhanced MRI when standard series are combined with the hepatobiliary phase for differentiation of FNH and HCA in lesions larger than 2 cm.

Characterization of hepatic adenoma and focal nodular hyperplasia with gadoxetic acid

PURPOSE

To characterize imaging features of histologically proven hepatic adenoma (HA) as well as histologically and/or radiologically proven focal nodular hyperplasia (FNH) using delayed hepatobiliary MR imaging with 0.05 mmol/kg gadoxetic acid.

MATERIALS AND METHODS

Five patients with six HAs with histological correlation were retrospectively identified on liver MRI studies performed with gadoxetic acid, and T1-weighted imaging acquired during the delayed hepatobiliary phase. Additionally, 23 patients with 34 radiologically diagnosed FNH lesions (interpreted without consideration of delayed imaging) were identified, two of which also had histological confirmation. Signal intensity ratios relative to adjacent liver were measured on selected imaging sequences.

RESULTS

All six hepatic adenomas (100%), which had histological confirmation, demonstrated hypointensity relative to adjacent liver on delayed imaging. Furthermore, all of the FNH (including 34 radiologically proven, 2 of which were also histologically proven) were either hyperintense (23/34, 68%) or isointense (11/34, 32%) relative to the adjacent liver on delayed imaging. None of the FNHs were hypointense relative to liver.

CONCLUSION

Distinct imaging characteristics of HA versus FNH on delayed gadoxetic acid-enhanced MRI, with adenomas being hypointense and FNH being iso- or hyperintense on delayed imaging may improve specificity for characterization, and aid in the differentiation of these two lesions.

Hepatocyte transporter expression in FNH and FNH-like nodule: correlation with signal intensity on gadoxetic acid enhanced magnetic resonance images

PURPOSE

Our aim was to evaluate the hepatocyte transporters in focal nodular hyperplasia (FNH) and FNH-like lesions and to correlate the grade of its expression with signal intensity on the hepatobiliary phase (HB phase) of gadoxetic-acid-enhanced magnetic resonance imaging (EOB-MRI).

MATERIALS AND METHODS

Thirteen histopathological confirmed cases including eight with EOB-MRI were studied. Immunohistochemical staining for transporter was performed and its grade semiquantitatively analyzed.

RESULTS

Histopathologically, ten cases showed almost equal organic anion transporter polypeptide (OATP) 8 expression relative to the surrounding liver; the remaining three showed stronger OATP8 expression. In eight cases with EOB-MRI, two demonstrated more hyperintensity on the HB phase, and their OATP8 expression was stronger compared with the surrounding liver. The remaining six cases showed isointensity on the HB phase and revealed almost equal OATP8 expression. The expression of export transporter multi-drug-resistant proteins (MRP) 1 and 2 were almost equal relative to the surrounding liver in most cases (11/12, 92 %; 11/12, 92 %, respectively), whereas MRP3 focally overexpressed in 75 % (9/12) of cases.

CONCLUSION

FNH and FNH-like nodules revealed equal or stronger OATP8 expression than background liver. OATP8 expression showed significant correlation with signal intensity on the HB phase.

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.

Diagnosis of well-differentiated hepatocellular lesions: role of immunohistochemistry and other ancillary techniques

There is considerable overlap in morphologic features in well-differentiated hepatocellular lesions necessitating the use of immunohistochemistry and other techniques for diagnosis. Map-like pattern with glutamine synthetase in focal nodular hyperplasia and cytoplasmic staining with serum amyloid associated protein in inflammatory hepatocellular adenoma (HA) are useful for this distinction. The distinction of well-differentiated hepatocellular carcinoma (HCC) and HA in noncirrhotic liver is facilitated by demonstrating glypican-3 and cytogenetic changes like gains of chromosomes 1 and 8. Nuclear staining with β-catenin and/or diffuse staining with glutamine synthetase strongly favors well-differentiated HCC or HA with high risk for HCC. In a cirrhotic liver, separation of early HCC from high-grade dysplastic nodule requires identification of stromal invasion, which can be highlighted by absence of keratin 7-positive ductular reaction. Combined use of heat shock protein 70, glutamine synthetase, and glypican-3 can be useful as positivity for 2 or more of these markers has shown high specificity for HCC in early studies.

Hepatocellular adenomas: current update on genetics, taxonomy, and management

Hepatocellular adenomas (HCAs) are uncommon, benign hepatocellular neoplasms that commonly occur in young women. Recent advances in pathology and cytogenetics have thrown fresh light on the pathogenesis of HCAs leading to classification of HCAs into 3 distinct subtypes, each with a characteristic epidemiology, histopathology, oncogenesis, and imaging findings. The aim of the article was to provide a comprehensive review of contemporary taxonomy of HCAs, with an emphasis on cross-sectional imaging findings and management.

Incidental Findings: A Case Study of Benign Liver Masses

Frequently, liver masses are found in the course of medical imaging examinations. This article presents a unique case study with multiple benign liver masses: hemangiomas, focal nodular hyperplasias (FNHs), and liver cell adenomas (LCAs). Most hemangiomas have a characteristic echogenic appearance on sonography and need no further workup. FNH may be difficult to visualize sonographically because it is composed of normal hepatocytes in an abnormal arrangement. LCAs and liver adenomatosis are more serious, requiring medical intervention and monitoring.

Tumors of the liver and intrahepatic bile ducts: radiologic-pathologic correlation

Primary tumors of the liver can be classified pathologically based on their cell of origin into epithelial tumors, arising from hepatocytes or biliary epithelium, and nonepithelial tumors, including mesenchymal tumors and lymphoma. Characteristic findings on MR imaging can be seen in many cases. This article reviews the MR imaging appearance of these tumors with pathologic correlation.

Adenoma or atypical hepatic focal nodular hyperplasia: role of preoperative imaging and laparoscopic treatment

Differentiation of focal nodular hyperplasia (FNH) and other hypervascular liver lesions, such as hepatocellular adenoma (HCA), is important because of the drastically different therapeutic approach. However, FNH can be well distinguished only if it shows a typical aspect; alternatively, in the case of atypical FNH, imaging findings are not specific enough to provide a secure diagnosis and histologic verification of the lesion is required. In addition, HCA cannot be identified conclusively by any current available imaging technique and it can be at best suspected strongly, and this suspicion may lead to liver resection. Herein we report a case of a patient with an unusual FNH nodule presenting at ultrasonographic scanning as an isoechoic mass arising from hepatic segment 4b; the diagnostic indecision between FNH and HCA was not definitively solved even after computed tomography scan and magnetic resonance imaging and the patient was scheduled for a laparoscopic resection. The pathologic examination diagnosed an atypical FNH nodule. The clinical doubt between FNH and HCA remains a problem affecting the clinicians, and more effort should be made in the direction of a better preoperative differentiation of such different conditions. Surgical resection should not be considered as the failure of the preoperative diagnostic attempt, but as the mainstay for a definitive and sure diagnosis.

The use of immunohistochemistry in liver tumors

A variety of benign and malignant neoplasms can be encountered in the liver. Hematoxylin and eosin-stained tissue sections alone may not yield sufficient information to definitively diagnose liver tumors; therefore, ancillary studies with immunohistochemical markers can play a crucial role in differentiating the different hepatic neoplasms. The recent development of oncofetoprotein glypican-3 has added to the value of immunohistochemistry in diagnosing liver cancer. This review discusses the immunohistochemical markers used most often in the diagnosis of hepatic tumors.

Spontaneous regression of focal nodular hyperplasia: a pathological report

Focal nodular hyperplasia (FNH) is a benign tumour of the liver, occurring in 0.6-3% of the general population. Most lesions are diagnosed incidentally. With the increasing use and improvement of diagnostic imaging, FNH is being observed more often. It has been shown, using radiological approaches, that most FNH remain stable, or even regress, over a long follow-up period. In addition, it is extremely rare that FNH were discovered in elderly. However, to our knowledge, there is no pathological report illustrating the regression of FNH. We report here a case showing the pathological changes occurring during the regression phase of FNH, with dense fibrous tissue mixed with arteries replacing hepatocytes nodules.

Molecular characterization of the vascular features of focal nodular hyperplasia and hepatocellular adenoma: a role for angiopoietin-1

Focal nodular hyperplasia (FNH) and hepatocellular adenoma (HCA) are two hepatic nodular lesions of different etiologies. FNH, a polyclonal lesion, is assumed to be a regenerative reaction following a vascular injury, whereas HCA is a monoclonal, benign neoplastic lesion. In addition to features that are predominantly found in either FNH or HCA (e.g., dystrophic vessels in FNH and single arteries in HCA), FNH and HCA share morphological vascular abnormalities such as dilated sinusoids. We hypothesized that these anomalous vascular features are associated with altered expression of growth factors involved in vascular remodeling. This was based on reports of morphologically abnormal hepatic vasculature and nodular lesions in transgenic models of hepatocytic overexpression of angiopoietin-1 (Ang-1), a member of the angiopoietin family, which is crucially involved in vascular morphogenesis and homeostasis. We investigated gene and protein expression of members of the angiopoietin system and vascular endothelial growth factor A (VEGF-A) and its receptors in 9 FNH samples, 13 HCA samples, and 9 histologically normal livers. In comparison with normal samples, a significant increase in Ang-1 was found in FNH (P < 0.01) and HCA (P < 0.05), whereas no significant changes in Ang-2, receptor tyrosine kinase with immunoglobulin-like and EGF-like domains 2, VEGF-A, or vascular endothelial growth factor receptor 2 (VEGFR-2) were observed.

CONCLUSION

Because of the different etiological contexts of a preceding vascular injury in FNH and a neoplastic growth in HCA, Ang-1 might exert different effects on the vasculature in these lesions. In FNH, it could predominantly stimulate recruitment of myofibroblasts and result in dystrophic vessels, whereas in HCA, it may drive vascular remodeling that produces enlarged vessels and arterial sprouting that generates single arteries.

Clonality and TP53 mutation analysis of focal nodular hyperplasia of the liver

Focal nodular hyperplasia (FNH) is considered a benign tumor of the liver. However, the biologic nature and clonality status of FNH are not well established. We sought to determine the clonality and TP53 mutation status of FNH to better characterize the nature of FNH. We analyzed 15 cases of FNH from female patients who underwent surgical resection of their lesions. Genomic DNA was extracted from paraffin-embedded tissue sections using laser-capture microdissection and analyzed for X-chromosome inactivation status and TP53 mutations by direct DNA sequencing. Thirteen cases were informative for X-chromosome inactivation analysis. Of the 13 informative cases, 4 (31%) showed a nonrandom pattern of X-chromosome inactivation, consistent with monoclonal origin. No TP53 mutations were detected in any of the FNH cases. The clonality status was not associated with any clinicopathologic parameters such as age and lesion size. Our data indicate that a significant proportion of FNH lesions have a monoclonal origin, suggesting that they are neoplastic rather than reactive.

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.

Focal nodular hyperplasia after orthotopic liver transplantation

Focal nodular hyperplasia (FNH) has been well characterized in native livers, but to our knowledge, no cases of FNH have been described in liver allografts. We review the clinicopathological features of 6 FNHs identified in 4 patients after orthotopic liver transplantation. There were 3 male patients and 1 female patient ranging in age from 2 to 63 years. The time from transplant to a diagnosis of FNH ranged from 15 to 118 months. Two patients presented with an incidental solitary liver nodule. One patient presented with 2 liver nodules, and the other patient initially presented with 1 liver nodule and was found to have another nodule at autopsy 6 years later. Two FNHs were seen as an incidental finding at autopsy, and the other 4 were initially identified on ultrasound. Follow-up magnetic resonance imaging and computed tomography scans revealed features atypical for FNH and suspicious for hepatocellular carcinoma. The initial diagnosis of FNH was made by needle core biopsy in 3 cases and at autopsy in 2 cases. The lesions ranged in size from 1.7 to 6.9 cm. Three patients had conditions associated with altered hepatic vascular perfusion; 2 patients had portal vein thrombosis, and 1 had a partial allograft from a living donor. In conclusion, FNH can present as a hepatic nodule after orthotopic liver transplantation and should not be confused with hepatocellular carcinoma. Because of altered hepatic circulation in the posttransplant liver, a diagnosis of FNH would not be unexpected. FNH should be considered in the differential diagnosis of hepatic nodules within the posttransplant liver, especially in patients with known hepatic vascular perfusion abnormalities.

[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.

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.

Unsaturated fatty acids promote hepatoma proliferation and progression through downregulation of the tumor suppressor PTEN

BACKGROUND/AIMS

The impact of dietary fatty acids on the development of cancers is highly controversial. We recently demonstrated that unsaturated fatty acids trigger the downregulation of the tumor suppressor PTEN through an mTOR/NF-kappaB-dependent mechanism in hepatocytes. In this study, we investigated whether unsaturated fatty acids promote hepatoma progression by downregulating PTEN expression.

METHODS

The effects of fatty acids and PTEN-specific siRNAs on proliferation, invasiveness and gene expression were assessed using HepG2 hepatoma cells. The tumor promoting activity of unsaturated fatty acids was evaluated in vivo using HepG2 xenografts in nude mice.

RESULTS

Incubation of HepG2 cells with unsaturated fatty acids, or PTEN-specific siRNAs, increased cell proliferation, cell migration and invasiveness, and altered the expression of genes involved in inflammation, epithelial-to-mesenchymal transition and carcinogenesis. These effects were dependent on PTEN expression levels and were prevented by mTOR and NF-kappaB inhibitors. Consistent with these data, the development and size of subcutaneous HepG2-derived tumors in nude mice xenografts were dramatically increased when mice were fed with an oleic acid-enriched diet, even in the absence of weight gain.

CONCLUSIONS

These data demonstrate that dietary unsaturated fatty acids promote hepatoma progression by reducing the expression of the tumor suppressor PTEN.

Multiple spontaneous liver cell adenomas of different types (liver adenomatosis)

In 1999, Nguyen et al divided focal nodular hyperplasia (FNH) in 2 groups, the classical and nonclassical. The former also included those cases of FNH with classical characteristics exhibited "on a subtle scale," whereas the latter included among others mainly the telangiectatic FNH (T-FNH) variant. Hepatocellular adenoma (HCA) was classically considered by definition a neoplasm with no ductal or ductular differentiation, but today the spectrum of HCA does include variant 3, which may have CK7+ ductules. Owing to genotypic-phenotypic correlation, T-FNH (synonymous with progressive FNH of others) is not considered yet as part of the spectrum of FNH, instead it is diagnosed as a variant of HCA, which now includes 4 variants. Variant-3, which may contain CK7+ ductules, and is also termed HCA with ductal/ductular differentiation, corresponds to T-FNH. Notwithstanding the nosologic advancement, and outside the "archetypal" types, the differential morphologic diagnosis of spontaneous HCA versus FNH may remain problematic as ductular proliferation in some cases of FNH may be scanty and hard to find. In some histologic overlapping cases of FNH and HCA the morphologic diagnosis may be very difficult or even impossible (especially in small lesions) and molecular biology may be of critical assistance. A prototypical case of surgically resected multiple spontaneous liver cell adenomas of various types, including HCA of T-FNH type and steatotic type, previously interpreted in different ways, affecting a young girl, is presented herein.

Over-expression of glutamine synthetase in focal nodular hyperplasia: a novel easy diagnostic tool in surgical pathology

BACKGROUND AND AIMS

Glutamine synthetase (GS) is a useful marker in tumour liver pathology, including hepatocellular adenomas and nodules in cirrhosis. We investigated the use of GS as a marker in various clinical situations, in which FNH diagnosis had been firmly established to determine its contribution to diagnosis.

METHODS

Seventy-nine cases of resected FNH, all on normal (or occasionally steatotic) livers, were retrieved from our collection. The control group was composed of hepatocellular adenomas and well-differentiated hepatocellular carcinoma. The following stains: H&E, Masson's trichrome, Gordon-Sweet, PAS, perls and immunostains: CK7 and 19, and GS were carried out. FNH was diagnosed based on traditional pathological techniques. In case of uncertainty, particularly with hepatocellular adenoma, additional immunostainings including liver fatty acid-binding protein, serum amyloid A and beta-catenin were performed.

RESULTS

Glutamine synthetase immunostaining was similar in all FNH cases. Positive GS staining of hepatocytic cytoplasms formed large areas, anastomosed in a 'map-like' pattern, often surrounding hepatic veins, whereas GS was not expressed in hepatocytes close to fibrotic bands containing arteries and ductules. In comparison, hepatocellular adenoma staining was completely different, even in cases of fibrotic bands due to tumour remodelling related to necrosis or haemorrhage. In hepatocellular adenomas or well-differentiated hepatocellular carcinoma presenting beta-catenin mutation, GS was positive but with a completely different pattern that appeared diffuse and not 'map-like'.

CONCLUSION

Regardless of the FNH size or steatotic content, GS produced a similar and characteristic pattern and consequently represents a good marker for easily identifying resected FNH from other hepatocellular nodules.

Natural course of hepatic focal nodular hyperplasia: a long-term follow-up study with sonography

PURPOSE

We aimed to investigate the natural course of hepatic focal nodular hyperplasia (FNH) in a long-term follow-up study with sonography.

METHOD

This study comprised 30 patients (24 women and 6 men) with 34 FNHs. Diagnosis of FNH was made using color Doppler sonography, contrast-enhanced CT, or MRI in combination with needle biopsy. Patients were followed every 3 to 6 months with sonography. Regression or progression of tumor was defined as a change of over 30% in maximal diameter. Disappearance was defined as no vizualization of the tumor on at least 3 follow-up sonographic examinations.

RESULTS

Thirty-four FNHs were followed over a mean period of 42 months (range, 7-95 months). Twenty-four lesions (70.6%) were stable in size, 1 (2.9%) progressed, and 9 (26.5%) regressed. Of those that regressed, 6 (17.6%) disappeared over a mean period of 59 +/- 30 months (range, 20-95 months). Older age (OR 1.26, 95% CI 1.02-1.56; p < 0.05) and longer follow-up time (OR 1.11, 95% CI 1.01-1.21; p < 0.05) were the independent factors associated with complete regression of FNH.

CONCLUSION

Most FNHs were stable or regressed/disappeared after a long follow-up period. Based on the benign course, conservative treatment for asymptomatic FNH should be advocated.

Telangiectatic adenoma - computed tomography and magnetic resonance findings: a case report and review of the literature

Telangiectatic adenoma is a new classification of a hepatic lesion. It was previously named telangiectatic focal nodular hyperplasia but it is in fact true adenoma with telangiectatic features. We report here a case of telangiectatic adenoma in a 72-year-old woman. The image features are lack of a central scar, a heterogeneous lesion, hyperintensity in T1-weighted MR images, strong hyperintensity in T2-weighted MR images, and persistent contrast enhancement in delayed-phase contrast-enhanced CT or T1-weighted MR images. It is a monoclonal lesion with potential of malignancy. The treatment of telangiectatic adenoma is surgery, the same way as hepatic adenoma. Focal nodular hyperplasia may be managed by clinical follow-up alone.

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.

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.

Hepatobiliary pathology

PURPOSE OF REVIEW

Studies are reviewed from the past year concerning the histopathology of liver and biliary diseases and their pathogenesis.

RECENT FINDINGS

Several cases of acute hepatitis E showed portal and periportal hepatitis, with polarization of neutrophils to the interface region and lymphocytes more centrally in the portal tracts. Transfection of hepatitis C virus into cultured fetal hepatocytes resulted in sustained growth of 50-90 nm diameter viral particles. The ductular reaction in nonalcoholic steatohepatitis appears to evolve with fibrosis in response to hepatocyte replicative senescence. Hepatocellular release of hepcidin is critical for iron homeostasis in a manner analogous to pancreatic insulin for glucose homeostasis; this 'endocrine' focus was elaborated in an overview of hemochromatosis. Specific microscopic features of liver-cell adenomas combined with genetic analysis for hepatocyte nuclear factor 1alpha and beta-catenin mutations allows differentiation into four variants. Steroid-sensitive biliary strictures resembling primary sclerosing cholangitis but with increased serum immunoglobulin G4 and infiltrating immunoglobulin G4-positive plasma cells ('immunoglobulin associated cholangitis') are part of a spectrum of disorders including autoimmune pancreatitis and inflammatory pseudotumor.

SUMMARY

Pathologic features of viral hepatitis C and E, immunohistochemistry for the ductular reaction and malignant liver tumors and several systemic disorders are among recent important pathology studies.

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.

Malignant transformation of hepatic adenomas

Hepatic adenomas are benign neoplasms of the liver that occur in several well-defined clinical settings, but principally that of excess hormone exposure. They have a small but poorly characterized risk of malignant degeneration. The clinical presentation and pathological findings were reviewed for all hepatic adenomas resected between January 1, 2003 and July 1, 2006. Immunohistochemistry for p53, beta-catenin and alpha-fetoprotein (AFP) were performed on those cases with malignant transformation and exon 3 of beta-catenin was amplified and sequenced. A total of 17 hepatic adenomas were resected and 3 showed malignant transformation. All three cases were in women with an age range of 23-33 years. The clinical presentations were vague abdominal pain. Histologically, the malignant transformation occurred within otherwise typical hepatic adenomas. Two of three cases showed patchy atypia throughout the hepatic adenoma. The hepatocellular carcinoma arose as distinct nodules directly within the adenomas, effectively ruling out synchronous lesions. The hepatocellular carcinomas were unifocal in two cases and multifocal in one case with the greatest dimensions of the hepatocellular carcinoma being 2.5, 2.2, and 1 cm. Immunostains for AFP and beta-catenin were negative in both the hepatic adenomas and areas of hepatocellular carcinoma. p53 immunostaining was positive within the areas of malignant transformation in one case. No mutations or deletions were seen in exon 3 of the beta-catenin gene for either the adenomas or the carcinoma. In conclusion, two of the cases that developed hepatocellular carcinomas showed cytological atypia in the background adenoma. The hepatocellular carcinomas arose as distinct nodules within the adenomas. No common molecular pathway of hepatocellular carcinogenesis was observed by examining AFP, beta-catenin, and p53 immunostains and no beta-catenin mutations or deletions were found.

Application of immunohistochemistry to liver and gastrointestinal neoplasms: liver, stomach, colon, and pancreas

CONTEXT

Immunohistochemistry has become an integral component of the practice of pathology. Newer antibodies allow for increasingly precise diagnoses for tumors that previously could not be easily identified. Recently, immunohistochemical evaluations have begun to allow pathologists to actively assist in determining prognosis and even in selecting therapies.

OBJECTIVE

To summarize the usefulness of currently available immunostains for the study of liver and gastrointestinal system neoplasms and to make recommendations for panels of immunostains that can be particularly helpful.

DATA SOURCES

Information has been collected from recent literature as well as from personal experience and practice.

CONCLUSIONS

Many immunostains are now available for the practicing pathologist that allow for increasing accuracy in diagnosis of liver and gastrointestinal tract neoplasms. Panels of immunostains can be used to differentiate between various tumors and also to identify site of origin in the case of a metastatic neoplasm. Immunostains that allow for prognostic determinations and for guidance in the selection of chemotherapeutic agents can also be used by pathologists to assist in the management of patients with malignant tumors affecting the liver and gastrointestinal tract.

Over-expression of glutamine synthase in focal nodular hyperplasia (part 1): early stages in the formation support the hypothesis of a focal hyper-arterialisation with venous (portal and hepatic) and biliary damage

Background

Most focal nodular hyperplasia (FNH) cases are diagnosed by chance. We studied a case of pre-FNH. We used glutamine synthase as an immunohistochemical marker for perivenous zones.

Results

Neither fibrotic scars nor hepatocytic nodules surrounded by fibrosis with a ductular reaction were observed in the sections studied. Most sections generally displayed preserved architecture. The glutamine synthase-positive hepatocyte areas were wider than those observed in non-tumoural surrounding liver, and they tended to extend outwards. Portal tracts bordering the nodule were more fibrotic, with an absence of portal veins and ducts and with arterial proliferation often in proximity with large draining veins; isolated arteries were present and hepatic veins were rare in the nodule. These features appeared prior to the identification of other major criteria characteristics of FNH, thus supporting the "hypothesis of Wanless".

Conclusion

The findings confirm that in FNH there is a portal tract injury leading to local portal vein injury. This leads to a cascade of events, including arterial venous shunts, ductular reaction, and scar formation.

Focal nodular hyperplasia and hepatic adenoma: differentiation with low-mechanical-index contrast-enhanced sonography

OBJECTIVE

The purpose of our study was to determine the differentiating features of focal nodular hyperplasia (FNH) and hepatic adenoma on contrast-enhanced sonography.

MATERIALS AND METHODS

Sixty-two patients who underwent contrast-enhanced sonography and were confirmed to have FNH (n = 43) or hepatic adenoma (n = 19) were assessed retrospectively for arterial phase enhancement, filling direction, stellate arteries, and portal phase enhancement. An algorithm was applied to these interpreted features to determine the contrast-enhanced sonography diagnosis.

RESULTS

All lesions were hypervascular in the arterial phase. Centrifugal filling was more common in FNH (39 and 32 of 43, 91% and 74% [reader 1 and reader 2]) than in adenoma (3 and 3 of 19, 16%). Centripetal or mixed filling was more common in adenoma (16 and 16 of 19, 84%) than in FNH (4 and 11 of 43, 9% and 26%) (p < 0.001, kappa = 0.61). Stellate arteries characterized FNH (29 and 26 of 43, 67% and 60%) but not adenoma (3 and 2 of 19, 16% and 11%) (p < 0.001, kappa = 0.36). Sustained portal phase enhancement was more common in FNH (37 and 39 of 43, 86% and 91%) than in adenoma (9 and 12 of 19, 47% and 63%) (p < 0.02, kappa = 0.79). The sensitivity, specificity, positive predictive value, and negative predictive value of sonography for diagnosing FNH were 95% and 86%, 74% and 79%, 89% and 90%, and 88% and 71%, (reader 1 and reader 2, respectively).

CONCLUSION

FNH is predicted on the basis of arterial phase centrifugal filling and stellate vascularity on contrast-enhanced sonography. Adenoma is less reliably predicted on the basis of centripetal or mixed filling without stellate vascularity. Sustained portal phase enhancement is more common in FNH than in adenoma but contributes less to the differentiation of these lesions.