Abstract: Objective The aim of this study was to summarize magnetic resonance imaging (MRI) manifestation of atypical focal nodular hyperplasia (FNH) of the liver. Methods 116 patients with liver FNH were encountered in our hospital between January 2022 and July 2024, all underwent plain, enhanced MRIscan, including diffusion weighted imaging (DWI), and the diagnosis was confirmed by biopsies or post-operational histo-pathological examinations. Results Of the 116 patients with liver FNHA, all had solitary intrahepatic nodule, located at right and/or left lobe, with diameters of 1.0to 11.2 cm, averaged with (6.1±1.3)cm, including≤2.0 cm in 31 cases, 2.0-5.0 cm in 51 cases and ＞5.0 cm in 34 cases; equal or slightly lower signals on T1WI, equal or slightly higher signals on T2WI, slightly higher signals on DWI, high signals at arterial phase, slightly high or equal signals at portal phase, equal or low signals at delayed phase, and high or equal signals at hepatobiliary phase; without central scar in 49lesions(42.2%),with pseudocapsule in 69lesions(59.5%),with internal bleeding or necrosis in 43lesions (37.1%),with fat infiltration in 37lesions (31.9%) and without significant enhancement at arterial phase in 56lesions(48.3%); percentages of without central scar, pseudocapsule, internal bleeding or necrosis, fat infiltration and non-significant enhancement at arterial phase in lesions >5.0cm were 64.7%, 88.2%, 61.8%, 52.9%and 73.5%, all significantly higher than 41.2%, 56.9%, 35.3%,31.4% and 47.1%(P＜0.05)in lesions of 2.0 to 5.0 cm or 19.4%, 32.3%, 12.9%, 9.7%and 22.6%(P＜0.05)in ≤2.0 cm of lesions. Conclusion Liver FNH, including atypical ones could have specific MRI feature, which might help clinicians make an appropriate measures to deal with.

Key words: Focal nodular hyperplasia of liver, Magnetic resonance imaging, Pathology, Diagnosis