Abstract: Objective To study the computed tomography (CT) and magnetic resonance (MR) imaging features of hepatic neuroendocrine carcinoma (NEC) in order to improve its diagnostic level.Methods The CT and MR imaging materials of 37 patients diagnosed as hepatic NEC by pathology and immunohistochemistry were retrospectively analyzed.Results Primary hepatic NECs were often single. Plain CT usually showed hypo-intense or mixed hypo-intense, and patchy high signals inside were observed when complicated with hemorrhage. In the enhanced scan, carcinomas showed gradually enhanced density. The CT values of solid lesions in portal phase and equilibrium phase were slightly higher than those in arterial phase. Usually primary hepatic NECs showed homogeneous or slightly higher thick-ring signals on MR diffusion-weighted imaging (DWI), slightly hyper-intense on T2-weighted imaging (T2WI) with some hyper-intense cystic zones inside, and slightly hypo-intense on T1-weighted imaging (T1WI) with some slightly hyper-intense lesions. The enhanced MR imaging of lesions showed moderate homogeneous enhancement or marginal enhancement with large arteries visible in some lesions, and iso-intensity or slightly hypo-intensity in portal and delayed phases. Some lesions showed complete or incomplete pseudo-capsule, and surrounding portal vein and hepatic vein were compressed without tumor thrombus. Liver metastatic NECs were often multiple and large. Plain CT scan showed hypo-intense or slightly hypo-intense. Compared with liver parenchyma, the enhanced scan of metastatic NECs usually showed heterogeneous enhancement or mild to moderate marginal enhancement in arterial phase, and iso-intense or slightly hypo-intense signals in portal and equilibrium phases. Meanwhile, liver metastatic NECs showed marginal hyperintensity on MR DWI, slightly hyper-intense on T2WI and slightly hypo-intense on T1WI, with cystic necrosis areas appearing in most of the lesions. The enhanced MR imaging showed heterogeneous or marginal enhancement in arterial phase and "eccentric target ring sign" in most of the portal and delayed phases. Tumor thrombi were visible in some portal veins.Conclusion Hepatic NECs can be divided into primary and metastatic tumors, whose imaging features have certain characteristics. Combined with clinical data and immunochemistry, CT and MR imaging are helpful for the diagnosis of lesions.

Key words: Liver neoplasms, Neuroendocrine carcinoma, Computed tomography, Magnetic resonance imaging