PRIMARY MALIGNANT-MELANOMA OF THE SINONASAL CAVITY - MR-IMAGING EVALUATION

To evaluate the magnetic resonance (MR) imaging characteristics of pri mary malignant melanoma of the sinonasal cavity, T1- and T2-weighted M R images of 12 patients with primary sinonasal melanoma were retrospec tively reviewed. Gadolinium-enhanced imaging was performed in seven ca ses, The MR images were compared with histopathologic results, There w ere seven melanotic melanomas and five amelanotic melanomas; hemorrhag e was present in three melanotic and two amelanotic melanomas. The sev en melanotic melanomas were hyperintense to gray matter on T1-weighted images (whether hemorrhage was present or not), consistent with the p aramagnetic effect of melanin. Four of the five amelanotic melanomas h ad intermediate signal intensity on T1-weighted images, one was not de tected. On T2-weighted images, all of the melanomas detected had inter mediate though variable signal intensity compared with that of gray ma tter, On gadolinium-enhanced images, all cases demonstrated mild to mo derate enhancement. The signal intensity of sinonasal melanoma appears to vary according to the histopathologic components of the tumor. Hig h signal intensity within the lesion on T1-weighted images suggests th e presence of melanin.