Duct-penetrating sign at MRCP: Usefulness for differentiating inflammatorypancreatic mass from pancreatic carcinomas

PURPOSE: To define the duct-penetrating sign at magnetic resonance (MR) cho langiopancreatography (MRCP) and to assess the usefulness of this sign for distinguishing an inflammatory pancreatic mass (IPM) from a conventional pa ncreatic carcinoma (CPC) compared with arterial phase computed tomography ( hereafter, CT) and arterial phase MR imaging (hereafter, MR imaging). MATERIALS AND METHODS: MRCP, CT, and MR images were compared by means of re ceiver operating characteristic (ROC) analysis for 11 IPMs and 43 CPCs. Wit h the MRCP images, a morphologic classification of the main pancreatic duct (MPD) was attempted for all lesions. On the basis of this classification a nd the enhancement patterns of a lesion, all readers graded the presence of IPM or CPC on a five-point scale for all images. RESULTS: On the MRCP images, the morphologic characteristics of the MPD wer e nonobstruction for IPM (28 of 33, 85%) and obstruction or irregular steno sis for CPC (124 of 129, 96%). At ROC analysis among all the techniques, MR CP images had the highest value (0.98) for significant areas under the ROC curve (CT, 0.84; MR, 0.76) (P <.001). For the duct-penetrating sign in the broad sense (nonobstructed MPD) and the sign in the narrow sense (only norm al MPD), the sensitivity, specificity, and accuracy for diagnosis of IPM we re 85%, 96%, and 94%, respectively, and 36%, 100%, and 87%, respectively. CONCLUSION: The duct-penetrating sign on MRCP images was more helpful to di stinguish IPM from CPC than were the enhancement patterns on CT and MR imag es.