Features of inflammatory pseudotumor in the maxillary sinus on CT and MRI

Objective To explore the features of inflammatory pseudotumor in the maxillary sinus on CT and MRI.Methods The CT and MRI data of 8 patients with histology-proven inflammatory pseudotumor in the maxillary sinus were retrospectively analyzed.All 8 patients underwent CT scans and 7 of them also underwent MRI examinations.In addition, the time-intensity curve (TIC) of dynamic contrast-enhanced (DCE)MR imaging were analyzed in 3 patients.Results Two cases had lesions in the left maxillary sinus, while the others showed lesions in the right maxillary sinus.All the lesions showed irregular shape with well-defined margins in 5 cases and hazy margins in 3 cases.The mean maximum diameter of the lesions was 51 mm (ranged from 29 mm to72 mm).On non-enhanced CT, the lesions were isodense to gray matter in 6 and slightly hypodense in 1 patients.Only 2 patients had post-contrast CT with moderate enhancement of their lesions.The lesions caused adjacent bony absorption and destruction with residual bony sclerosis.On MR T_1 WI, inflammatory pseudotumor showed hypointense in 2 patients and isointense in 5 cases in relative to gray matter.On T_2 WI, the lesions revealed inhomogeneous hypointense in 6 patients and isointense in 1 patients.Inflammatory pseudotumor showed heterogeneously slight contrast enhancement in 2 cases and moderate enhancement in 5 cases.The TIC showed a steady enhancement pattern in 3 patients.The lesions extended to nasal cavity in 6 cases, pterygopalatine fossa and infratemporal fossa in 4, orbit in 4, and cheek in 3 cases.Six patients underwent follow-up for 2-5 years after surgery and 2 of them were found to have recurrence.In comparison to CT, MRI was proved to show the extent of the lesions more clearly.Conclusions Bony destruction with sclerosis and hypointense signal on MR T_2 WI are typical manifestations of inflammatory pseudotumor in the maxillary sinus.Combined CT and MRI can provide clinicians with more comprehensive information for the diagnosis, therapy, and follow-up of these lesions. Key words: Cranuloma, plasma cell;  Maxillary sinus neoplasms;  Tomography, X-ray computed;  Magnetic resonance imaging