Characterization Of Hepatocellular Adenoma Based On The Phenotypic Classification

Hepatocellular adenomas (HCAs) are benign tumors rarely seen in clinical practice. The risk factor of the disease is not fully understood. Mainly, it is considered to be strongly associated with the long period use of oral contraceptives (OCs). The disease is mostly seen in women of child-bearing period. Its incidence is estimated to be0.1per year per100,000in non-OC users, and reaches3to4per100,000in long-term OC users. HCAs have an increased proclivity to hemorrhage and rarely undergo malignant transformation, and this makes a difference between HCA and other benign liver tumors such as hepatic hemangioma and focal nodular hyperplasia (FNH). Although the risk of hemorrhage and malignant transformation is low, sometimes the consequence is catastrophic. Tumor rupture may lead to intraperitoneal bleeding with hypovolemic shock. Hence, a better understanding of its natural history, ways of effective diagnosis, and proper management of the disease are of clinical importance.Hepatocellular adenoma is not a single disease but a heterogeneous group of tumors. Genetic alterations such as biallelic inactivation of hepatocyte nuclear factor-1a (HNF1a), activation of β-catenin of Wnt/β-catenin pathway, and the gain-of-function mutation of gp130involving in the Interleukin6(IL6) signal transduction has been recently detected. Based on the analysis of genotype-phenotype association, HCAs are currently categorized into four subtypes:(a) HNF1α inactivated HCA (H-HCA);(b)(3-catenin activated HCA (β-HCA);(c) Inflammatory HCA(I-HCA);(d) HCAs remain unclassified. Distinct characteristics of HCA subtypes, in term of natural history, and clinical, imaging, histopathological features have been observed. It is reported that, HCAs can be reliably classified with the help of a panel of immunohistochemical markers. Although this classification is new and is not widely accepted, it has definitive diagnostic and management implications, and is with an advantage of its simplicity. In China, epidemiologically, HCAs are mainly seen in men, and female patients rarely have a history of OC use, which is different from Europe and North America. The subclassification of HCAs in China has not been reported until now.Hepatic progenitor cells (HPCs) are considered to be the offspring of activated hepatic stem cells. HPCs retain their bipotency and can differentiate into hepatocytic and biliary lineages. Morphologically, HPCs are characterized by ovoid nucleus, small size (relative to hepatocytes), and scant basophilic cytoplasm. Multicenter studies revealed that HPCs express molecular markers in common with bile duct cells, fetal and adult hepatocytes. Although the cell origin of HCA has not been fully elucidated, some reports suggest that HPCs may involve in the development of HCA. Through immunohistochemistry, researchers observed the presence of HPCs and intermediate hepatocyte-like cells in half of the studied hepatocellular adenomas.In this article, we did a clinical analysis of pathologically confirmed HCA cases of Zhongshan hospital of recent years, summarized their clinical characteristics, diagnostic methods and management modes, in order to give clinicians some valuable indications. Through immunohistochemistry, we applied the phenotypic classification system to our group of study, and illustrated the state of HCA subtypes in China, in aspects of subtype proportion, clinical characters and histopathological characters. Finally, we analyzed correlation of the occurrence rate of hepatic progenitor cells and HCA subtypes.Part Ⅰ. Clinical analysis of hepatocellular adenomaObjective:To analyze the clinical features of hepatocellular adenoma, discuss methods of diagnosis and modes of management.Methods:From January2000to December2010,36cases with pathologically confirmed diagnosis of HCA in Zhongshan hospital were collected. Data of clinical manifestation, laboratory test, imaging, diagnosis and ways of treatment were retrospectively analyzed. Follow-up time was6months to10years.Results:In this group, tissue samples were retrieved from tumor resection in35cases, and from needle biopsy in the left one case. All cases were with confirmed pathological diagnosis of HCA. The cases included16men and20women. The age of patients ranged from16to69, with an average age of34.4. A history of oral contraceptive use was found in one patient, glycogen storage disease was present in3cases. Four patients had a history of HBV infection, and one patient had a history of HCV infection. Most cases (66.7%) were asymptomatic. Results of laboratory tests were mainly normal. The results of CT and MRI showed that the lesions were strongly enhanced on arterial phase, and the contrast enhancement quickly washed out on portal venous phase and delayed phase. The accurate rate of preoperative diagnosis were5.6%(2/36). Spontaneous tumor rupture and hemoperitoneum were observed in three patients, and four patients were complicated with atypical dysplasia or canceration. Hepatectomy was performed on33patients, allograft liver transplantation was performed on two patients, and one patient underwent transcatheter arterial chemoembolization only. All patients were followed up for6months to10years, and patients who had undergone complete resection were with no recurrence.Conclusions:The occurrence of HCA is commonly latent, clinical manifestations and imaging examinations are poor in specificity. It is not easy to make a confirmed diagnosis before surgery. Pathological diagnosis is the gold standard. Resection seems to be the primary choice for therapy.Part Ⅱ. Classification and characterization of hepatocellular adenomaObjective:To characterize HCA samples in China based on the phenotypic classification system, make comparison between our results and reports from oversea peers, and evaluate the phenotypic classification system.Methods:Formalin fixed and paraffin embedded tissue samples of30cases from2002to2011, whose tumors were surgically resected and pathologically diagnosed as HCA, were retrieved from the archived of the department of pathology, Zhongshan hospital. Ten serial sections,4-μm thick, were cut from each block. One section of each case were processed routinely for histopathological study, and the remainders were immunohistochemically stained with following markers:liver-fatty acid binding protein(L-FABP), glutamine synthetase (GS), β-catenin, serum amyloid A(SAA), and C-reactive protein (CRP). Patterns of immunohistochemical stain were interpreted, HCAs were classified; clinical and pathological features of cases were recorded; correlation between classification and feature of HCA were analyzed. Follow-up time was3months to9years.Results:Of all30cases (20female), we identified nine hepatocyte nuclear factor (HNF)-1α-inactivated HCA (30%), three β-catenin-activated HCA (10%), eleven inflammatory HCA (36.7%) and seven unclassified HCA (23.3%). Among inflammatory HCA group, two adenomas also presented β-catenin-activation. The use of oral contraceptives was only found in one41-year-old patient at her twenties. Homogeneous steatosis (6/9), microadenomas (2/9) were more frequently observed in HNF1a-inactivated HCA. Body mass index>25(5/11), alcohol use (4/11), and steatosis in nontumor liver (3/11) were more frequent in inflammatory HCA. The tumor was larger in β-catenin-activated HCA than in other subgroups.Conclusions:The clinical and pathological characteristics of HCA subgroups in China are mainly in accordance with those from Europe. A lower female proportion may be due to the scarcity of oral contraceptive use in China.Part Ⅲ. The relevance of occurrence rate of hepatic progenitor cells in HCAs and HCA subtypesObjective:To explore the relevance of occurrence rate of hepatic progenitor cells in HCAs and HCA subtypes.Methods:Slides of cases from previous section were immunohistochemically stained with progenitor-cell-specific markers:cytokeratin (CK)7, CK19, CK8, CK18. The occurrence rate, distribution pattern, and relevance to HCA subtypes of hepatic progenitor cells were analyzed.Results:Hepatic progenitor cells were observed in17of30HCAs. These17tumors also contained intermediate hepatocyte-like cells. The occurrence rate of hepatic progenitor cells in each HCA subtype were as follows:H-HCA6/9(66.7%), β-HCA3/3(100%), I-HCA5/11(45.5%), unclassified HCA3/7(42.9%). The occurrence rate of hepatic progenitor cells in each HCA subtype did not reach statistical significance. Hepatic progenitor cells in inflammatory HCAs mainly located in reactive bile ductules, which presented overlapping features of HCA and FNH.Conclusions:The high occurrence rate of hepatic progenitor cells in β-HCA may be associated with the activation of β-catenin. Hepatic progenitor cells in inflammatory HCAs may be relatively more primitive, and are capable of differentiating toward both hepatic and biliary lineage.