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. 2021 May 18;2(6):100183. doi: 10.1016/j.jtocrr.2021.100183

Table 1.

Clinical and Radiographic Characteristics of Enhancing CNS Lesions

Lesion Type Common Clinical Features Common Radiographic Features
Tumor progression Nodular growth on sequential imaging ≥3 mo apart
Progression in systemic disease
Rounded with either homogeneous or ring enhancement and clear delineation of lesion edge
Perilesional edema
Higher rCBV on perfusion imaging
Higher Cho/Cr and Cho/NAA on MRS
FDG PET of limited value
Potential role for amino acid PET
ICI-related pseudoprogression Growth within weeks of ICI initiation
Regression on sequential imaging separated by ≤3 mo
Clinical stability
Can be indistinguishable from tumor progression
Radiation necrosis More often found ≥6 mo after radiation therapy
Increased incidence after ICI therapy
May spontaneously regress on longitudinal imaging even if presenting with symptoms
Rim-enhancing pseudopodic lesion with central necrosis on T1-postcontrast
Perilesional edema of previous SRS target on FLAIR
Lower rCBV on PWI
Lower Cho/Cr and Cho/NAA on MRS
Demyelinating lesion History of autoimmune disease
History of high-dose or high-brain volume radiation therapy
Little to no growth on longitudinal imaging
T2 hyperintense, T1 hypointense
Little to no surrounding edema
Juxtacortical, periventricular
Homogenous enhancements; however, heterogeneous, nodular, ring-like (typically open ring), or tumefactive patterns may be found

Cho, choline; CNS, central nervous system; Cr, creatine; FDG, 18F-2-fluoro-2-deoxy-D-glucose; FLAIR, fluid-attenuated inversion recovery; ICI, immune checkpoint inhibitor; MR, magnetic resonance; MRS, magnetic resonance spectroscopy; NAA, N-acetyl aspartate; PET, positron emission tomography; PWI, perfusion-weighted imaging; rCBV, relative cerebral blood volume; SRS, stereotactic radiosurgery.