Comparison of MRI Features of Epithelioid Hepatic Angiomyolipoma and Hepatocellular Carcinoma: Imaging Data From Two Centers

Introduction: Epi-HAML easily misdiagnosed as malignant tumors like HCC because of low fat content. We analysed the magnetic resonance imaging (MRI) features of epithelioid hepatic angiomyolipoma (Epi-HAML), which would be helpful for the diagnosis of this disease. Methods: Thirty Epi-HAML patients were performed MRI unenhanced scan and three-phase contrast-enhanced MRI scan, among them, 25 cases were performed diffusion weighted imaging (DWI) sequence. The clinical and imaging features of patients were summarized. Images were analyzed by two abdominal radiologists independently. Results: Among the 30 Epi-HAML patients, 8 were males and 22 were females, resulting in the male-to-female ratio of 1:3. The age of onset ranged from 27 to 67 years, with an average of 47.87±10.33 years. Twenty-one of these 30 patients (70.0%) showed asymptomatic, while the remaining 9 (30.0%) displayed non-specific symptoms. In this study, Epi-HAML was a single mass (100%), which frequently occurred in the right lobe (60.0%) and manifested as a well-defined mass (93.3%) with regular shape (73.3%). The axial great diameter of tumor ranged from 0.9 to 7.4 cm, with an average of 3.86±1.90 cm. Twenty-eight cases showed hypointensity on T1WI (96.7%) and slight hyperintensity on T2WI (93.3%). Additionally, 12 cases (40.0%) with fat, 2 cases (6.7%) with bleeding, and 1 case (3.3%) with necrosis were confirmed. On contrast-enhanced MRI, Epi-HAML manifested as sever enhancement (100%) on the whole during the arterial phase. Meanwhile, 9 cases (30.0%) with draining hepatic vein and 12 cases (40.0%) with intra-tumor vessel were also detected. Additionally, 11 cases (36.7%) with intra-tumor vessel and 6 cases (20.0%) with capsule were also confirmed during the delayed phase. Specifically, the Epi-HAML presented as prolonged enhancement in 16 cases (53.3%), followed by wash out pattern in 10 cases (33.3%) and fade in 4 cases (13.3%). Conclusion: Epi-HAML frequently occurs in the middle-aged female, which usually lacks the clinical symptoms. Typically, Epi-HAML generally presents as an isolated and well-defined tumor with rich blood supply. Specifically, intra-tumor fat, intra-tumor vessel, drainage hepatic vein, lack of capsule and prolonged enhancement on MRI may contribute to the diagnosis of Epi-HAML.