Ring-Enhancing Lesions

Case A: There is a 3-cm left parietal lesion with a thin, T2 hypointense peripheral rim, smooth enhancement, prominent surrounding edema, and central restricted diffusion. Of note, the ring of peripheral enhancement is slightly thicker toward its cortical margin.

Case B: There are multiple supratentorial white matter T2 hyperintense lesions. The largest lesion in the left parietal lobe measures 2.7 cm and demonstrates a thin, smooth, incomplete rim of enhancement. Despite the size of this lesion, a paucity of surrounding edema and mass effect is noted. There is restricted diffusion in the periphery of the lesion but not in the center. Lesions in the right frontal and right occipital lobe also enhance.

Case C: A 2.2-cm right cerebellar ring-enhancing lesion without associated restricted diffusion is identified. Of note, there is an enhancing internal septation as well as irregularity, nodularity, and varying thickness of the enhancing wall.

Case D: A 5-cm, heterogeneous right occipital mass demonstrates a thick and nodular rim of enhancement. No internal restricted diffusion is noted. However, DWI hyperintensity associated with the enhancing rim suggests hypercellularity. Subtle ependymal enhancement is noted along the walls of the temporal horn of the right lateral ventricle. Marked surrounding edema and mass effect are noted.

Case E: This patient was receiving long-term immunosuppression. There is a 1.1-cm ring-enhancing lesion centered in the posterior left middle frontal gyrus with surrounding edema. There is mildly restricted diffusion in the rim of the lesion but not in the center. There is minimal surrounding linear enhancement along perivascular spaces as well as overlying dural enhancement.