Preoperative differentiation of primary central nervous system lymphomas (PCNSLs) and glioblastomas is of high clinical relevance because treatment strategies for glioblastoma and PCNSL vary substantially. In patients with glioblastoma, gross total resection followed by radiation therapy and chemotherapy with temozolomide is the treatment of choice, whereas patients with PCNSL usually undergo stereotactic biopsy followed by high dose methotrexate-based chemotherapy.
Standard magnetic resonance (MR) imaging sequences allow differentiation for most patients because PCNSL in immunocompetent patients usually appears as a homogeneous enhancement on contrast material–enhanced T1-weighted MR images, but glioblastomas usually exhibit a ring or ringlike zone of contrast enhancement around a hypointense central area of necrosis. A T2 hyperintense edema surrounds both tumors. Diffusion weighted imaging a well established advanced an MR technique has been reported to improve the differential diagnosis between PCNSL and GBM. Water diffusion can be measured with a parameter of apparent diffusion coefficient (ADC). Highly cellular tumors like PCNSL show areas of restricted diffusion with low ADC values, thus ADC is regarded as a marker of tumor cellularity.