Central nervous system lymphoma not detectable on single-photon emission CT with thallium 201.

A 33-year-old man with acquired immunodeficiency syndrome had an erosive supraglottic mass visible on CT scans of the neck; biopsy was postponed because of the patient's debilitated condition. Two weeks later, he was admitted with altered mental status; an MR image of the brain obtained at that time showed multiple bilateral mass lesions, the largest of which was 5 cm. Findings on a thallium-201 single-photon emission CT (SPECT) scan of the brain were normal. Ten days later, the patient died and autopsy showed both the neck and the brain lesions to be large-cell lymphoma. This case is counterevidence to the reported 100% sensitivity of thallium-201 brain SPECT for demonstrating lymphoma of the central nervous system.