Role of MR in the differentiation of IgG4-related from non-IgG4-related hepatic inflammatory pseudotumor

BACKGROUND: Hepatic inflammatory pseudotumor (IPT)is classified into 2 types based on IgG4 stain: IgG4-related and non-IgG4-related; the two types differ not only in their pathological characteristics, but also in the clinical features. This study aimed to investigate the MR character of hepatic IPT,and differentiate the IgG4-related IPT from the non-IgG4-related IPT.METHODS: Twenty-five patients with 27 histologically proven hepatic IPTs were retrospectively analyzed. Ten lesions were diagnosed as IgG4-related IPT, and the other17 as non-IgG4-related IPT. The MR signal features on T1,T2-weighted, dynamic-enhanced, and diffusion-weighted imaging were evaluated and compared.RESULTS: The dominant lesions were subcapsularly distributed(n=17, 63.0%) with clear boundary (n=20, 74.1%), and showed progressive enhancement pattern (n=21, 77.8%) with diffuse homogeneous (n=12, 44.4%) or heterogeneous (n=8,29.6%) hyperintensity, accompanied by delayed capsule-like enhancement (n=17, 63.0%) and central nonenhanced areas(n=18, 66.7%).