MRI of hepatic epithelioid hemangioendothelioma (HEH)
To investigate magnetic resonance imaging (MRI) characteristics of hepatic epithelioid hemangionendothelioma (HEH). The study was exempted from formal Ethics Committee approval due to its retrospective and noninvasive nature. Eleven patients with histology-proven HEH were collected from six different institutions in a 5-year time period. In all patients a contrast-enhanced MR study was available. Two experienced reviewers in consensus retrospectively noted potential MR findings of HEH. Reviewers separately analyzed morphological findings, tumor signal intensity, HEH contrast enhancement pattern, and tumor appearance on hepatobiliary phase and diffusion-weighted imaging (DWI). The frequency of various findings was calculated. The most frequent presentation was a peripheral distribution of the lesions (72.7%), target appearance on T2-weighted images (63.6%), low signal intensity on T1-weighted images (63.6%), ring or target-like enhancement at dynamic study (63.6%), and coalescence of nodules and capsular retraction (45.4%). Lack of hepatobiliary enhancement (5/8 patients) or "entrapment" hepatobiliary enhancement (3/8 patients) as well as target appearance at DWI (5/6 patients) was also observed in our series. Although quite variable imaging appearances were seen, a target appearance on the T2-weighted image, ring or target enhancement at dynamic study, lack of enhancement or "entrapment" at hepatobiliary phase, and target appearance on DWI are frequent findings of HEH.