Differentiation between inflammatory myofibroblastic tumor and cholangiocarcinoma manifesting as target appearance on gadoxetic acid-enhanced MRI

Purpose To determine the differential features of inflammatory myofibroblastic tumor (IMT) and intrahepatic cholangiocarcinoma (ICC) manifesting as target appearance on gadoxetic acid-enhanced MRI. Methods Twenty-seven patients with 36 IMTs (1.2–6.0 cm) and 34 patients with 34 ICCs (1.5–6.0 cm) who underwent gadoxetic acid-enhanced MRI were enrolled in this study. Two reviewers evaluated morphology, signal intensity, and enhancement features of tumors on T1-weighted imaging (T1WI), T2-weighted imaging (T2WI), diffusion-weighted imaging (DWI), and gadoxetic acid-enhanced imaging. Results As for 32 IMTs with target appearance, IMTs most commonly demonstrated early target appearance characterized by a peripheral hypointense rim on unenhanced T1WI ( n = 27, 84.4%), central enhanced area with a hypointense rim on arterial phase (AP) and portal venous phase (PVP) ( n = 29, 90.6%), and transitional phase (TP) ( n = 28, 87.5%). Meanwhile, most of the ICCs showed homogeneous hypointensity on T1WI (100%), a hyperenhancing rim on AP, late target appearance on TP ( n = 32, 94.1%) and HBP ( n = 32, 94.1%). Target appearance on DWI appearing as hyperintensity with central hypointense area was seen in 2 IMTs and 32 ICCs. On T2WI, 24 IMTs ( n = 24, 75.0%) displayed central iso- and peripheral hyperintensity and 27 ICCs (84.4%) showed layered hyperintensity with either brighter or darker area in center. The remaining six IMTs with no target were observed as cystic appearing nodules ( n = 3) or ill-defined hypovascular nodules ( n = 2) and fibrotic mass ( n = 1). Conclusion IMTs often show early target appearance on unenhanced T1WI, and early dynamic phases of gadoxetic acid-enhanced MRI. Target appearance on later phases, such as TP and HBP, and DWI target appearance were commonly in ICCs, but rare in IMTs.