PurposeThis study aimed to investigate the feasibility of diffusion-weighted imaging (DWI) in combination with conventional MRI features to differentiate sinonasal malignant melanoma (SNMM) from sinonasal squamous cell carcinoma (SNSCC).MethodsA total of 37 patients with SNMM and 44 patients with SNSCC were retrospectively reviewed. Conventional MRI features and apparent diffusion coefficients (ADCs) were evaluated independently by two experienced head and neck radiologists. ADCs were obtained from two different regions of interest (ROIs) including maximum slice (MS) and small solid sample (SSS). Multivariate logistic regression analysis was performed to identify significant MR imaging features in discriminating between SNMM and SNSCC. Receiver operating characteristic (ROC) curves were used to assess the diagnostic performance.ResultsSNMMs were more frequently located in the nasal cavity, with well-defined border, T1 Septate Pattern (T1-SP) and heterogeneous T1 hyperintensity, whereas SNSCCs were more frequently located in the paranasal sinus, with homogenous T1 isointensity, ill-defined border, reticular or linear T2 hyperintensity, and pterygopalatine fossa or orbital involvement (all p < 0.05). The mean ADCs of SNMM (MS ADC, 0.85 x 10(-3)mm(2)/s; SSS ADC, 0.69 x 10(-3)mm(2)/s) were significantly lower than those of SNSCC (MS ADC, 1.05 x 10(-3)mm(2)/s; SSS ADC, 0.82 x 10(-3)mm(2)/s) (p < 0.05). With a combination of location, T1 signal intensity, reticular or linear T2 hyperintensity, and a cut-off MS ADC of 0.87 x 10(-3)mm(2)/s, the sensitivity, specificity, and AUC were 97.3%, 68.2%, and 0.89, respectively.ConclusionDWI combined with conventional MRI can effectively improve the diagnostic performance in differentiating SNMM from SNSCC.