Differentiating pancreatic neuroendocrine tumors from pancreatic ductal adenocarcinomas by the "Duct-Road Sign" A preliminary magnetic resonance imaging study

To assess the duct-road sign and tumor-to-duct ratio (TDR) in MRI for differentiating pancreatic neuroendocrine tumors (PNETs) from pancreatic ductal-adenocarcinomas (PDACs). Retrospectively reviewed MRI characteristics of 78 pancreatic masses (histopathology-proven 25 PNETs and 53 PDACs). Receiver operating characteristics with TDR and diagnostic performance of the duct-road sign for differential diagnosis were performed. The prevalence of duct-road sign in PNETs was higher than that for PDACs (84% vs 0%; P<.001). A strong correlation (r= 0.884, P<.001) wasobserved betweenMRI forPNETs and the frequency of this sign. Performance characteristics of the duct-road sign inMRI for PNET diagnosis were sensitivity (84%, [21 of 25]), specificity (100%, [53 of 53]), positive predictive value (100%, [21 of 21]), negative predictive value (92.9%, [53 of 57]), and accuracy (94.8%, [74 of 78]). In the intention-to-diagnose analysis, the corresponding values were 67.7%(21 of 31), 100%(53 of 53), 100%(21 of 21), 84.1%(53 of 63), and 88.1%(74 of 84). TheTDRinPNETs was observed to be greater than that in PDACs (14.6 +/- 9.3 vs 6.9 +/- 3.8, P=. 001). TDR with a cut-off value of 7.7 had high sensitivity (84%) and specificity (66%) with area under curve (0.802, 95% CI: 0.699, 0.904; P<.001) for distinguishing PNETs from PDACs. The presence of duct-road sign and TDR > 7.7 on MRI may assist in diagnosis for PNET instead of PDAC.