Spectrum of appearances on CT and MRI of hepatic epithelioid hemangioendothelioma

Background: This study aims to analyze the computed tomography (CT) and magnetic resonance imaging(MRI) characteristics of hepatic epithelioid hemangioendothelioma (HEHE). Methods: Eleven patients with histopathologically confirmed HEHE via surgical excision or biopsy were included. Imaging findings of these 11 patients were retrospectively analyzed (CT images obtained from all patients and MR images from five patients). Patterns of growth, characteristics of distribution, density/signal features, patterns of contrast enhancement, and changes of adjacent tissues were evaluated. Results: HEHE is characterized by multiple lesions in the liver. HEHE could be further categorized as three types when considering patterns of growth: nodular type(5 cases), coalescent type(1 case) and mixed type(5 cases). In this study, a total of 312 lesions were detected, 214(74.3 %) of which were subcapsular. All lesions appeared as hypodense while round lower density were found within 10 lesions(< 2 cm) on unenhanced CT images. On MRI, all lesions demonstrated low signal intensity on T1 weighted images and high heterogeneous signal intensity on T2 weighted images when compared to the normal liver parenchyma. Other imaging features included "lollipop sign"(6 cases) and capsular retraction(6 cases). On contrast-enhanced CT and MRI, lesions smaller than 2.0 cm mostly showed mild homogeneous enhancement (214/227, 94.3 %); lesions measuring 2.0-3.0 cm in diameter showed ring-like enhancement (16/53,30.2 %) and heterogeneous delayed enhancement (29/53,54.7 %); lesions larger than 3.0 cm demonstrated heterogeneous delayed enhancement (26/32, 81.3 %). Conclusion: The imaging findings of HEHE showed some typical imaging features and size-dependent patterns with contrast enhancement on both CT and MR images, these features can be used for accurate imaging diagnosis of HEHE.