Computed tomography and magnetic resonance imaging features of lipid-rich neuroendocrine tumors of the pancreas

AIM:To clarify the computed tomography(CT) and magnetic resonance imaging(MRI) characteristics of lipid-rich pancreatic neuroendocrine tumors(Pan NETs).METHODS:Enhanced CT and MRI performed before pancreatectomy in 29 patients with 34 histologicallyconfirmed Pan NETs was retrospectively reviewed. Tumor attenuation on CT and signal intensities on conventional(T1- and T2-weighted) and chemical shift MRI were qualitatively analyzed and compared alongside adipose differentiation-related protein(ADRP) immunostaining(ADRP-positive:lipid-rich; ADRP-negative:non-lipid-rich) results using Fisher’s exact test or the Mann-Whitney U test. Signal intensity index on chemical shift MRI was quantitatively assessed.RESULTS:There were 15 lipid-rich Pan NETs(44.1%) in 12 patients(41.4%). Tumor attenuation during the early,portal venous,and delayed phases of enhanced CT(P = 0.888,0.443,and 0.359,respectively) and signal intensities on conventional MRI(P = 0.698 and 0.798,respectively) were not significantly differentbetween lipid-rich and non-lipid-rich Pan NETs. Four of the 15 lipid-rich Pan NETs exhibited high signal intensity on subtraction chemical shift MRI,and the association of high signal intensity on subtraction imaging with lipid-rich Pan NETs was significant(4 of 15 lipid-rich Pan NETs,26.73%,vs 0 of 19 non-lipid-rich Pan NETs,0%,P = 0.029). Lipid-rich Pan NETs showed a significantly higher signal intensity index than non-lipidrich Pan NETs(0.6% ± 14.1% vs-10.4% ± 14.4%,P = 0.004). Eight of 15 lipid-rich Pan NETs,vs 0 of 19 nonlipid-rich Pan NETs,had positive signal intensity index values in concordance with lipid contents.C O N C L U S I O N :C T c o n t ra s t e n h a n c e m e n t a n d conventional MR signal intensities are similar in lipidrich and non-lipid-rich Pan NETs. Chemical shift MRI can demonstrate cytoplasmic lipids in Pan NETs.