A 36-yr-old man with AIDS exhibited intense Tl-201 uptake (lesion-to-b
rain uptake ratio 5.38) in a brain lesion previously detected by MRI a
nd CT. The lesion was biopsied and found to contain cells with viral i
nclusions diagnostic of cytomegalovirus infection, not tumor as the th
allium SPECT results suggested, Thallium-201 SPECT may be less specifi
c than previously reported for differentiating neoplastic disease from
opportunistic infections in AIDS patients.