Multiple sclerosis simulating brain tumor on computed tomography.

A 44-year-old woman with multiple sclerosis (MS) stimulating a brain tumor on CT is reported. At the first hospitalization, a heterogeneously enhancing mass lesion with perifocal edema was identified on CT in the left parietal lobe. Biopsy of the lesion revealed necrotic change of the brain, gliosis, and perivascular cuffing; several months later no tumor cells were identified. The follow-up CT revealed reduction of the enhancing lesion and disappearance of the perifocal edema, with only a low density area persisting. At the second hospitalization, CT revealed a ring enhancing lesion with perifocal edema in the right temporoparietal region. Follow-up CT several months later revealed reduction of the lesion, with the residual of a small low density area. Magnetic resonance (MR) allowed us to identify multiple lesions in addition to those visualized on CT. In some cases of MS, the CT findings are very similar to those found in brain tumors. In these instances, MR is more useful in the diagnosis of MS than CT.