Positron emission computed tomography and magnetic resonance imaging features of sinonasal small round blue cell tumors

Aim: The sinonasal tract hosts numerous types of undifferentiated neoplasms, having small round cell morphology. The aim of this study was to determine whether sinonasal small round blue cell tumors (SRBCT) have distinct imaging features on computed tomography (CT), magnetic resonance imaging (MRI), and 18-fluorodeoxyglucose positron emission tomography (¹⁸F-FDG PET)/CT. Methods: Seventy-three patients (43 male; M_age = 61.2 years) with histopathologically proven sinonasal SRBCT were retrospectively reviewed. Imaging features of SRBCTs including location, maximum dimension, margin characteristics, presence of calcification, sclerotic bone changes, intratumoral necrosis, tumor extension, bone destruction, bone remodeling, perineural spread, T1- and T2-weighted MRI signal intensity, qualitative features on diffusion-weighted imaging and ¹⁸F-FDG PET/CT, and pattern of contrast enhancement were analyzed using Fisher’s exact test or the chi-square test. The maximum standardized uptake values (SUV_max) and apparent diffusion coefficient (ADC_mean) values of SRBCT were compared by utilizing the Kruskal–Wallis test. Results: There was a significant difference between SRBCT type regarding the tumor location (p = 0.006), ¹⁸F-FDG uptake pattern (p = 0.006), involvement of the orbit (p = 0.016) and pterygopalatine fossa (p = 0.043), the presence of perineural spread (p < 0.001), bone destruction (p = 0.034), and intratumoral necrosis (p = 0.022). Bone destruction and necrosis were more common in rhabdomyosarcoma. Perineural spread was common in sinonasal adenoid cystic carcinoma (ACC). Qualitative ¹⁸F-FDG uptake features as well as tumor location were significantly different between sinonasal ACC and sinonasal undifferentiated carcinoma. The ADC_mean and SUV_max values were not statistically different between SRBCT types. Conclusions: Sinonasal SRBCTs have numerous distinct imaging features on CT, MRI, and ¹⁸F-FDG PET/CT that could be useful in the differentiation between lesions when the histopathologic diagnosis is inconclusive.