MRI features of primary hepatic neuroendocrine tumor

Abstract

Objective To investigate the MRI features of primary hepatic neuroendocrine tumor (PHNET). Methods Clinical information and MR imaging features of 13 histopathologically confirmed PHNET patients were retrospectively reviewed. All patients underwent routine MRI examination including T2WI and chemical shift imaging, diffusion weighted imaging (DWI) and dynamic contrast-enhanced imaging. All lesions were divided into two groups according to the maximum diameter (≥ 30 mm for large lesion group and<30 mm for small lesion group). The following MRI features of lesions were evaluated: location, size, growth pattern, signal intensity (T1WI, T2WI, DWI, in-and opposed-phase) and dynamic contrast-enhancement pattern. The pathologic features were also analyzed. Results The PHNET can be single lesion (n= 7) or multiple lesions (n=6) in which 4 cases showed diffuse pattern. One hundred and six lesions in 13 patients were detected. The median diameter of all lesions was 20 mm (ranging from 3 to 200 mm). Fourteen lesions were found in ≥30 mm group and 92 lesions in<30 mm group. (1) In ≥30 mm group, all lesions had well-defined margin, heterogeneous hyperintensity on T2WI, heterogeneous hypointensity on T1WI and halo sign on DWI. All lesions showed cystic degeneration, necrosis and pseudo-capsule. Three lesions showed dilation of bile duct around the lesion, and three lesions hemorrhaged and three lesions signal dropped on out-of-phase. On arterial phase, 7 lesions showed ring-like enhancement, and the other 7 lesions showed heterogeneous enhancement;then on portal venous phase and delayed phase, 8 lesions showed persistent enhancement and the other 6 lesions showedwash-outappearance. Three cases showed lymphadenopathy in the peritoneum and liver hilum. (2) In<30 mm group, 76 lesions showed well-circumscribed edge and the other 16 lesions had ill-defined margin. Eighty two lesions showed relatively homogeneous hyperintensity on T2WI and relatively homogeneous hypointensity on T1WI. One lesion showed heterogeneous hyperintensity on T2WI and heterogeneous hypointensity on T1WI. Nine lesions showed halo and nodular hyperintensity and the other 83 lesions nodular hyperintensity on DWI. Ten lesions demonstrated cystic degeneration and necrosis. Ten lesions showed pseudocapsule. All lesions showed no dilation of bile duct, hemorrhage and signal drop on out-of-phase. On arterial phase, 31 lesions showed ring-like enhancement, 3 lesions showed heterogeneous enhancement and 58 lesions showed homogeneous enhancement;on portal venous phase and delayed phase, 62 lesions showed persistent enhancement and 30 lesions showedwash-outsign. No lymphadenopathy was found in this group. In the pathologic analysis, hemorrhage and central necrosis were detected in the gross specimens. And in the 13 cases of PHNET, 1, 3 and 9 cases were classified into G1, G2 and G3 grade, respectively. Conclusions The PHNET can be single or multiple with various sizes. The large lesions often show heterogeneous signal intensity on T2WI and T1WI with cystic degeneration, necrosis, hemorrhage, pseudo-capsule and dilated bile duct, peripheral hyperintensity on DWI, ring-enhancement or heterogeneous slight enhancement in arterial phase, while small lesions often show ring-enhancement or homogeneous obvious enhancement in arterial phase. Key words: Liver neoplasms; Neuroendocrine tumor; Magnetic resonance imaging