MR imaging of multiple sclerosis simulating brain tumor

Multiple sclerosis may sometimes present as a mass lesion that is indistinguishable from brain tumor both clinically and radiologically. We describe two cases of multiple sclerosis simulating brain tumor on computed tomography (CT) scans and magnetic resonance (MR) images, one of which was proved and another was suggestive to be demyelinating disease by biopsy. Steroid therapy produced regression of the lesions of MR images and CT scans. Our cases and others in the literature suggest strategies for detecting multiple sclerosis presenting as a mass lesion.