Magnetic resonance imaging findings of inverted papilloma: Differential diagnosis with malignant sinonasal tumors

Background: Computed tomography and magnetic resonance imaging (MRI) are the techniques of choice for pretreatment staging in neoplasms of the sinonasal tract. In inverted papilloma (IP), the information provided by computed tomography regarding characterization of the lesion is rather nonspecific. The present retrospective study was performed in the attempt to identify distinguishing features of IP on MRI. Methods: MRI examinations of 23 patients affected by IP (16 primary and 7 recurrent) and 23 patients affected by malignant tumors (MT; 12 adenocarcinomas, 9 squamous cell carcinomas, and 2 neuroendocrine carcinomas) of the sinonasal tract were evaluated. IP arose from the lateral nasal wall in 17 cases, the maxillary sinus in 5 cases, and the nasal septum in 1 case. The signal intensity of IP and MT was compared with muscles on spin-echo (SE) T2 and SE T1 images; contrast enhancement was compared with nasal septum mucosa. Possible specific MRI patterns in the two groups of patients ...