Manifestations of Hepatic Focal Nodular Hyperplasia in Hepatobiliary Phase of Enhancement by Hepatocyte-specific Contrast Agent: Comparison With Pathologic Findings
Authors: Xu Jiangfeng , Zhang Liqing , Li Jianxun , Cui Xiaojian , Jiang Qingping , Zhang Yan 
Published: September 2021

Abstract
Background: To explore the signals and diagnostic value of hepatic focal nodular hyperplasia (FNH) in the hepatobiliary phase of gadolinium-ethoxybenzyl-diethylenetriamine-pentaacetic acid (Gd-EOB-DTPA) enhanced MRI.Methods: Imaging data of 43 pathologically proven FNH lesions from 39 patients who underwent Gd-EOB-DTPA enhanced MRI scanning at our hospital between January 2016 and June 2019 were retrospectively analyzed. The signal characteristics in the hepatobiliary phase were analyzed and compared with the pathologic findings.Results: According to the characteristics of signals in the hepatobiliary phase, the signals were classified as follows: homogenous iso-high intensity signals in 20.93% (9/43) lesions, heterogeneous iso-high intensity signals in 67.44% (29/43) lesions, homogenous low-intensity signals in 4.65% (2/43) lesions, and heterogeneous low-intensity signals in 6.98% (3/43) lesions. Two patients were with multiple lesions, where one was with 2 lesions of heterogeneous high-intensity signals, and the other with 3 lesions of heterogeneous low-intensity signals. Pathologic findings were as follows: the slices of the 38 lesions with high-intensity signals in a hepatobiliary phase were with hyperplasic hepatocytes, inflammatory cell infiltration, and malformed blood vessels. Twenty-nine of the lesions were with fiber tissues of different degrees and were classified as classic type. The remaining 9 lesions were without fibrous scars and were classified as non-classic type. The other 5 of the 43 lesions were non-classic FNH with no evident fibrous tissues, while 4 of them were with >40% steatosis in the hyperplasic hepatocytes; the immunohistochemistry showed CK7(-)/CK19(-) in 1 lesion and β-catenin (nucleus +) in another lesion. Comparisons of pathologic with imaging findings were as follows: twenty-nine lesions were with heterogeneous iso-high intensity signals, of which the slices showed evident fibrous tissues of different degrees, and the slices of 9 lesions with homogenous iso-high intensity signals in the hepatobiliary phase showed no fibrous tissues. Three lesions with heterogeneous low-intensity signals in the hepatobiliary phase showed about 80% mixed steatosis in hyperplasic hepatocytes. The other two lesions both showed homogeneous low-intensity signals in the hepatobiliary phase, where 1 lesion was with >40% macrovesicular steatosis and CK7/CK19 (-), while the other only showed β-catenin (nucleus +) by immunohistochemistry. Conclusions: The signals of FNH in the hepatobiliary phase showed various characteristics, where the signal differences were mainly associated with the number of hyperplastic hepatocytes in lesions, presence of steatosis, fibrous scars, and conditions of small bile ducts, and potentially associated with β-catenin (nucleus+). Low-intensity signals were relatively rare for FNH, thus representing a relatively major challenge for diagnosing this type FNH.