PET-avid hepatocellular adenomas: incidental findings associated with HNF1-α mutated lesions

Insights into hepatocellular adenomas in Asia: molecular subtypes, clinical characteristics, imaging features, and hepatocellular carcinoma risks

Hepatocellular adenomas (HCAs) are benign monoclonal liver tumors. Advances in molecular studies have led to the identification of distinct subtypes of HCA with unique pathways, clinical characteristics, and complication risks, underscoring the need for precise diagnosis and tailored management. Malignant transformation and bleeding remain significant concerns. Imaging plays a crucial role in the identification of these subtypes, offering a non-invasive method to guide clinical decision-making. Most studies involving patients with HCAs have been conducted in Western populations; however, the number of studies focused on Asian population has increased in recent years. HCAs exhibit distinct features in Asian population, such as a higher prevalence among male patients and specific subtypes (e.g., inflammatory HCAs). Current clinical guidelines are predominantly influenced by Western data, which may not fully capture these regional differences in epidemiology and subtype distribution. Therefore, this review presents the updated molecular classification of HCAs and their epidemiologic differences between Asian and Western populations, and discuss the role of imaging techniques, particularly magnetic resonance imaging using hepatobiliary contrast agents, in classifying the subtypes and predicting the risk of hepatocellular carcinoma.

Hepatocellular adenoma update: diagnosis, molecular classification, and clinical course

Hepatocellular adenomas (HCA) are acquired focal liver lesions, that occur mainly in young-to-middle-aged women who are on long-term estrogen-containing contraceptives or young men after prolonged use of anabolic steroids. Furthermore, distinct underlying diseases, such as obesity, metabolic dysfunction-associated steatotic liver disease, glycogen storage disease, etc. are considered risk factors. The 2017 Bordeaux classification, in particular Nault et al, divided HCAs into eight subtypes according to their pheno- and genotypic characteristics. This includes HCAs with hepatocyte-nuclear-factor (HNF1-alpha mutation), HCAs with β-catenin mutation, and HCAs without either of these genetic mutations, which are further subdivided into HCAs with and without inflammatory cells. HCAs should no longer be classified as purely benign without histologic workup since three of the eight subtypes are considered high-risk lesions, requiring adequate management: malignant transformation of the pure (ßex3-HCA) and mixed inflammatory/β-catenin exon 3 (ßex3-IHCA) adenomas, as well as potential bleeding of the sonic hedgehog HCA and pure (ßex7/8-HCA) and mixed inflammatory/β-catenin exon 7/8 (ßex7/8-IHCA). Elective surgery is recommended for any HCA in a male, or for any HCA exceeding 5 cm. Although MRI can classify up to 80% of adenomas, if findings are equivocal, biopsy remains the reference standard for adenoma subtype.

Steatotic hepatocellular adenoma: an unusual cause of a hypermetabolic liver lesion

A 22-year-old woman with a history of surgically treated pelvic teratoma and solid liver lesion in the extension study. Radiological follow-up was decided. This liver lesion experienced a progressive increase in size, reaching 6 cm. Contrast-enhanced liver MRI was performed, revealing a heterogeneous mass in the right hepatic lobe with non-hepatocyte-like behaviour. With this information, the following entities were ruled out: haemangioma, adenoma, hepatocarcinoma and focal nodular hyperplasia. Given that it could be a teratoma metastasis, a tumour of any other origin or a non-tumoral lesion with no hepatocyte component, it was decided to perform a 2-[18F]FDG PET/CT scan. It showed the liver mass with notable glycolytic hypermetabolism, suggestive of malignancy. In a multidisciplinary committee, it was decided to perform a laparoscopic right hepatectomy. Pathological examination revealed a benign hepatocytic lesion compatible with a steatotic adenoma.

Hepatocellular Adenomas: Molecular Basis and Multimodality Imaging Update

Hepatocellular adenomas (HCAs) are a family of liver tumors that are associated with variable prognoses. Since the initial description of these tumors, the classification of HCAs has expanded and now includes eight distinct genotypic subtypes based on molecular analysis findings. These genotypic subtypes have unique derangements in their cellular biologic makeup that determine their clinical course and may allow noninvasive identification of certain subtypes. Multiphasic MRI performed with hepatobiliary contrast agents remains the best method to noninvasively detect, characterize, and monitor HCAs. HCAs are generally hypointense during the hepatobiliary phase; the β-catenin-mutated exon 3 subtype and up to a third of inflammatory HCAs are the exception to this characterization. It is important to understand the appearances of HCAs beyond their depictions at MRI, as these tumors are typically identified with other imaging modalities first. The two most feared related complications are bleeding and malignant transformation to hepatocellular carcinoma, although the risk of these complications depends on tumor size, subtype, and clinical factors. Elective surgical resection is recommended for HCAs that are persistently larger than 5 cm, adenomas of any size in men, and all β-catenin-mutated exon 3 HCAs. Thermal ablation and transarterial embolization are potential alternatives to surgical resection. In the acute setting of a ruptured HCA, patients typically undergo transarterial embolization with or without delayed surgical resection. This update on HCAs includes a review of radiologic-pathologic correlations by subtype and imaging modality, related complications, and management recommendations. ^© RSNA, 2023 Online supplemental material is available for this article. Quiz questions for this article are available through the Online Learning Center.

Steatotic Hepatitis Presenting as a Huge Hypermetabolic Liver Mass

ABSTRACT

FDG PET/CT scan is a diagnostic imaging modality for oncologic patients, but with false-positive findings in inflammatory diseases. In this interesting case, we present a 24-year-old woman with history of giant cell tumor of the bone (lumbar vertebrae) who underwent whole-body FDG PET/CT scan for treatment response evaluation. FDG PET/CT scan demonstrated a large hypermetabolic tumoral mass lesion in segment VI/VII of the right hepatic lobe. A range of malignant versus benign lesions should be considered as differential diagnoses, including metastasis, primary cholangiocarcinoma, hepatocellular carcinoma, focal nodular hyperplasia, and infection. Final diagnosis of "steatotic hepatitis" after CT-guided biopsy was established.

A Scoping Review of the Classification, Diagnosis, and Management of Hepatic Adenomas

BACKGROUND

Hepatic adenomas (HA), or hepatocellular adenomas, are benign, solid liver lesions that develop in otherwise normal livers, often in the setting of increased estrogen levels. While considered a benign tumor, there is a risk for substantial complications such as hemorrhage and malignant transformation. We review the diagnosis, classification, and potential therapeutic management options for patients with HA.

METHODS

A scoping narrative review was conducted based on recent literature regarding classification, diagnosis, and management of HA.

RESULTS

While HAs are typically considered benign, complications such as hemorrhage and malignant transformation may occur in approximately 25% and 5% of patients, respectively. Recent advances in imaging and molecular profiling have allowed for the classification of HAs into subtypes allowing for patient risk stratification that helps guide management. Surgical resection should be considered in asymptomatic patients who are male, have an adenoma ≥5 cm in diameter, or have the β-catenin-activated subtype due to an increased risk of hemorrhage and/or malignant transformation.

CONCLUSION

Molecular profiling has aided in the stratification of patients relative to the risk of complications to predict better the potential behavior of HAs.

False-positive 18F fluorodeoxyglucose positron emission tomography-avid benign hepatic tumor: Previously unreported in a male patient

We report a case of ¹⁸F fluorodeoxyglucose (FDG) positron emission tomography (PET)–computed tomography-avid histologically confirmed inflammatory hepatic adenoma in a 77-year-old male patient without any history of steroid, alcohol use. This is the first case report of inflammatory hepatic adenoma in a male patient documented in the published literature showing uptake on ¹⁸F-FDG PET. Previous single case report of ¹⁸F-FDG PET-avid hepatic adenoma in a male patient was of hepatocyte nuclear factor-1-α subtype.

18F-FDG PET/CT of hepatocellular adenoma subtypes and review of literature

INTRODUCTION

This study evaluates 18F-FDG PET/CT imaging characteristics of pathologically proven hepatocellular adenoma (HCA) subtypes.

METHODS

This is a retrospective review of an institutional database (2011-2017) for subjects with a pathologic diagnosis of hepatic adenomas established within 6 months of a pre-treatment 18F-FDG PET/CT exam. An expert pathological review by a hepatopathologist was performed to confirm diagnosis and subtype HCA. A review of the 18F-FDG PET/CT exams was performed by two board-certified nuclear radiologists in consensus. Corresponding demographic and clinical data were obtained by electronic chart review.

RESULTS

Nine subjects were identified. An HCA subtype was established in seven subjects (4 HNF1A-mutated and 3 Inflammatory). The mean HCA lesion size was 2.8 cm (range 0.6-6.2, SD 2.0) with a mean SUVmax of 5.9 (range 2.1-18.9, SD 5.1). The SUV values of HNF1A-mutated HCA were significantly higher than inflammatory HCA: lesion SUVmax (5.3 ± 1.48 vs. 2.8 ± 0.59, p < 0.033), lesion-to-liver SUVmax ratio (1.4 ± 0.22 vs. 0.8 ± 0.21, p = 0.031), lesion SUVmean (3.6 ± 0.37 vs. 2.0 ± 0.46, p = 0.0086).

CONCLUSION

HNF1A-mutated HCA may have greater SUV values than inflammatory HCA on 18F-FDG PET/CT exams. However, there are contradictory data in the literature and further investigation is warranted.

18-F Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography of a Large Inflammatory-Hepatocellular Adenoma

We report a case of an 81-year-old male evaluated for a liver space-occupying lesion. US-guided biopsy and immunohistochemistry were suggestive of hepatocellular adenoma (HCA)-inflammatory (with telangiectasia). Serial 18-F fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography scans revealed a heterogeneously enhancing hypermetabolic mass in the right lobe of the liver, remaining stable for a span of 3 years. This case highlights that benign rare tumors of the liver such as HCA can be intensely FDG avid and that uptake cannot conclude its malignant transformation.

FDG-PET/CT imaging findings of hepatic tumors and tumor-like lesions based on molecular background

The usefulness of whole-body 18-fluoro-2-deoxyglucose (FDG)-fluorodeoxyglucose positron emission (PET)/computed tomography (CT) is established for assessment of disease staging, detection of early disease recurrence, therapeutic evaluation, and predicting prognosis in various malignancies; and for evaluating the spread of inflammation. However, the role of FDG-PET/CT for the liver is limited because CT and magnetic resonance imaging (MRI) can provide an accurate diagnosis of most tumors. In addition, in other potentially useful roles there are several pitfalls in the interpretation of FDG uptake in PET/CT imaging. Accurate evaluation demands knowledge of the FDG uptake of each lesion, including potential negative and positive uptakes, and requires an understanding of the underlying background of the molecular mechanisms. The degree of FDG uptake is dependent on cellular metabolic rate and the expression of glucose transporter, hexokinase, and glucose-6-phosphatase, which in turn are closely affected by biological characteristics such as pathological category (e.g., adenocarcinoma, squamous cell carcinoma, small cell cancer, transitional cell cancer, neuroendocrine tumor, sarcoma, lymphoma), tumor differentiation, histological behavior (e.g., solid, cystic, mucinous), and intratumoral alterations (e.g., necrosis, degeneration, hemorrhage). Correlation with the CT and MRI findings, which also precisely depict the pathological findings, is important to avoid misdiagnosis.

Current Approaches in the Management of Hepatic Adenomas

INTRODUCTION

Hepatic adenomas (HAs) are a benign and relatively rare type of liver neoplasms. We review the diagnosis, evaluation, and potential therapeutic management options for patients with HA.

METHODS

A comprehensive review of the English literature was performed utilizing MEDLINE/PubMed and Web of Science databases with end of search date the 30th April of 2018. In PubMed, the terms "hepatocellular," "hepatic," "liver," and "adenoma," "adenomatosis" were searched in the title and/or abstract.

RESULTS

Recent advances in molecular classification of HA have determined distinct subtypes with specific clinical, pathological, and imaging characteristics. In general, cessation of exogenous hormonal administration or weight loss may lead to HA regression. Surgical resection, either open or laparoscopic, should be considered in patients with symptoms and risk factors for hemorrhage or malignant transformation. These risk factors include tumor diameter greater than 5 cm, β-catenin activated subtype, and/or male gender. The management of acute hemorrhage should primarily aim at achieving hemodynamic stability via angioembolization followed by elective resection, whereas malignant transformation is treated according to oncologic resection principles. Although pregnancy is one of the known risk factors for tumor growth and associated complications, the presence of an HA per se should not be considered a contradiction to pregnancy.

CONCLUSION

Future genomic-based multicenter studies are required to provide a strong basis for formulating an evidence-based risk-adapted model that guides individualized management strategies for patients with HA.

18-Fluoro-deoxyglucose uptake in inflammatory hepatic adenoma: A case report

Positron emission tomography computed tomography (PET-CT) using 18-Fluoro-deoxyglucose (¹⁸FDG) is an imaging modality that reflects cellular glucose metabolism. Most cancers show an uptake of ¹⁸FDG and benign tumors do not usually behave in such a way. The authors report herein the case of a 38-year-old female patient with a past medical history of cervical intraepithelial neoplasia and pheochromocytoma, in whom a liver lesion had been detected with PET-CT. The tumor was laparoscopically resected and the diagnosis of inflammatory hepatic adenoma was confirmed. This is the first description of an inflammatory hepatic adenoma with an ¹⁸FDG up-take.

Hepatocyte nuclear factor 1α-inactivated hepatocellular adenomas exhibit high (18)F-fludeoxyglucose uptake associated with glucose-6-phosphate transporter inactivation

OBJECTIVE

This immunohistochemical study aimed to elucidate the molecular mechanism underlying the increased fluorine-18 fludeoxyglucose (FDG) uptake in hepatocyte nuclear factor 1α (HNF1α)-inactivated hepatocellular adenomas (H-HCAs).

METHODS

Three resected H-HCAs were studied using FDG positron emission tomography. Each maximum standardized uptake value (SUVmax) was determined. Resected samples were subjected to immunohistochemical staining for the following glucose metabolism-related proteins: glucose transporter 1 (GLUT1) and glucose transporter 2 (GLUT2), indicative of uptake and transport of glucose into cellular cytoplasm; hexokinase 2 (HK2) and hexokinase 4 (HK4), glucose phosphorylation; glucose-6-phosphate transporter 1 (G6PT1), uptake and transport of glucose-6-phosphate into endoplasmic reticulum; and glucose-6-phosphatase (G6Pase), dephosphorylation.

RESULTS

All three H-HCAs exhibited increased FDG intake, with an average SUVmax of 6.6 (range: 5.2-8.2). No sample expressed GLUT1 and HK2; all the samples exhibited equivalent GLUT2 and HK4 expression, equivalent or slightly increased G6Pase expression and significantly decreased G6PT1 expression relative to the non-neoplastic hepatocytes of background liver.

CONCLUSION

The increased FDG uptake observed in H-HCAs is associated with GLUT2 and HK4 expression and G6PT1 inactivation.

ADVANCES IN KNOWLEDGE

H-HCA exhibits a high FDG uptake owing to the inactivation of G6PT1, which is transcriptionally regulated by HNF1α.