MR imaging and CT features of oncocytic papilloma of the sinonasal tract with comparison to inverted papilloma.

OBJECTIVE:: To evaluate and compare the imaging feature of sinonasal oncocytic papilloma (OP) with inverted papilloma (IP).

METHODS:: The CT and MR imaging manifestations of 17 pathology proven sinonasal OPs were reviewed and compared with 17 IPs randomly selected as a control group over the same period.

RESULTS:: Seventeen sinonasal OPs had unilateral occurrence and 16 of them (94.1%) had a lobulated configuration.The distribution of original sites differed significantly between OPs and IPs (p < 0.05).OPs (47.1%) particularly involved the maxillary sinus,while IPs (64.7%) usually arose from the lateral nasal wall.OPs exhibited isointense in 5 cases and grape- or patchy-like hyperintense in 12 on T1  weighted image, and isointense in 13 and hyperintense in 4 on T2 weighted image, with moderate enhancement. 10 OPs appeared as a Type II time intensity curve (TIC).There was significant difference of pre-contrast T1 signal intensity between OPs and IPs (p < 0.05).The prevalence of the imaging findings of "focal osteitis" (11.8% vs 94.1%) and "cystic change" (94.1% vs 17.6%) differed significantly between OPs and IPs (p < 0.05), but not for "cerebriform"sign (82.4% vs 94.1%) (p > 0.05).

CONCLUSION:: Three imaging features including high signal on T1  weighted image, cystic change and only a rare association of focal osteitis may help the diagnosis of OP distinguished from IP.

ADVANCES IN KNOWLEDGE:: The typical imaging characteristics should prompt an accurate diagnosis of sinonasal OPs in routine clinical practice. Combination of CT and MR imaging characteristics can be more helpful in discriminating OPs from IPs.