BACKGROUND: Although histological diagnosis is indispensable in treating @entity149 ( @entity149 ), we sometimes face an intractable situation in which tissue can be obtained only from a deep-seated @entity75 . In place of a histological diagnosis, the diagnostic adequacy of the combined use of @entity419 PET and corticosteroid administration for @entity149 located in a deep-seated brain structure is reported. METHODS: @entity1 with a @entity5 were treated as having @entity149 without histological confirmation, based on the following criteria: (1) there was no evidence of systemic @entity5 ; (2) the @entity5 showed an extremely high FDG uptake relative to normal gray matter on pretreatment @entity419 PET; (3) the @entity5 decreased in size 1  week after diagnostic therapy by @entity228 administration on contrast-enhanced T1-weighted magnetic resonance imaging (MRI). FDG uptake of the lesion was evaluated by the maximum of standardized uptake values (SUVmax) and @entity5 -to-normal ratio of the SUV (T/N ratio). The extent of the @entity5 reduction was calculated by volumetric analysis for the treatment response to corticosteroid administration. RESULTS: Ten @entity1 (4 males and 6 females) matched these criteria. On pretreatment @entity419 PET, mean SUVmax in the @entity5 was 24.8 (8.75-60.75), and mean T/N ratio was 3.24 (2.17-5.12). The extent of @entity5 volume reduction was shown to be 21 to 68  % 1  week after diagnostic therapy by @entity288 . Mean total dose and duration of @entity288 were 719  mg as @entity617 and 6.5  days, respectively. Nine @entity1 achieved complete response and one @entity1 achieved partial response on MRI after standard treatment for @entity149 with high-dose @entity1499 and/or whole-brain irradiation. CONCLUSION: Although the value of biopsy is universal, combining @entity419 PET and corticosteroid administration is an important alternative method that may lead to the diagnosis of deep-seated PCNSLs in cases with intractable histopathological confirmations.

Combined use of XXXX PET and corticosteroid for diagnosis of @entity149 without histopathological confirmation.

@entity1 :: ('9606', 'Species') :: ['Patients', 'patients', 'patient'] @entity419 :: ('MESH:D019788', 'Chemical') :: ['18  F-FDG'] @entity75 :: ('MESH:D001927', 'Disease') :: ['brain lesion'] @entity5 :: ('MESH:D009369', 'Disease') :: ['tumor', 'deep-seated tumor', 'malignancy'] @entity149 :: ('MESH:D002493', 'Disease') :: ['PCNSL', 'primary central nervous system lymphoma'] @entity228 :: ('CHEBI:50858', 'Chemical') :: ['corticosteroid'] @entity1499 :: ('MESH:D008727', 'Chemical') :: ['methotrexate'] @entity617 :: ('MESH:D011239', 'Chemical') :: ['prednisolone'] @entity288 :: ('MESH:D000305', 'Chemical') :: ['corticosteroids']
@entity419 :: (MESH:D019788,Chemical) :: ['18  F-FDG']
