Diffusion restriction of posterior uveal melanoma on MR imaging

A 55-year-old male with clinical and opthalmological signs of retinal ablation was referred for orbital magnetic resonance imaging (MRI). MR scan revealed a small tumor nodule in the posterolateral part of left eye globe as a cause of ablation. Tumor showed high signal on transverse diffusion weighted image (DWI) (Fig. A, arrow), low signal on apparent diffusion coefficient image (Fig. B, arrow), consistent with restricted diffusion. The nodule had intermediate signal on T1 sagittal weighted unenhanced image (Fig. C, arrow). The patient underwent left eye enucleation with histopathologically proved uveal melanoma.