Diagnosis: May be very helpful in assessing tumor grade (and hence prognosis) in patients with as uncharacterized masses. Also may help direct biopsy to most malignant part of tumor since FDG uptake is directly related to tumor grade. Also may be extremely useful in HIV patients with indeterminate abnormalities on MRI to differentiate lymphoma from infectious lesions such as toxoplasmosis.

Staging: No role.

Restaging/Surveillance: PET is the single most useful test in the differentiation of therapy-induced changes (on MRI) from recurrences.