A multimodal diagnostic approach to inverted papilloma: Proposal of a novel diagnostic flow-chart

Purpose: Inverted papilloma (IP) is a tumor usually arising from sinonasal cavities, with tendency for recurrence and possible malignant transformation. Along with endoscopy, computed tomography (CT) and magnetic resonance imaging (MRI) play a crucial role in defining preoperative staging, tumor origin, and possible differential diagnosis, with significant repercussions on therapeutic planning. However, at present no consensus has been reached concerning IP diagnostic workup. Aim of this study is to assess CT and MRI sensitivity and specificity in identifying IP imaging hallmarks, evaluating their global diagnostic accuracy in order to define a novel diagnostic flowchart. Methods: We retrospectively analyzed multimodal imaging of patients with histologically confirmed IP and mimics. Two neuroradiologists in consensus retrospectively rated the presence of typical imaging features of IP, both on CT and MRI scans. Sensitivity, specificity and diagnostic accuracy were assessed for both the techniques. Final results were expressed as ROC curves and relative areas under the curve (AUC). Results: The AUC considering CT parameters were 0.42, whereas the AUC considering MRI parameters were 0.54. Combining the 2 techniques and limiting the evaluation to the most distinctive features such as focal hyperostosis and CCP, the AUC was 0.79. Conclusion: MRI can provide better tissue characterization and higher diagnostic accuracy in case of suspected IP, whereas CT is more useful in determining bony involvement. Here we propose a possible diagnostic flowchart for IP, based on the assumption that the combination of the imaging techniques allows to optimize the clinical assessment and the subsequent therapeutic planning.