Primary diffuse large B-cell lymphoma of the CNS is an aggressive neoplasm with poor prognosis. Treatment consists of steroids, high-dose methotrexate, and radiation. Tumor resection does not improve survival, only causes further neurologic deficits, and is not recommended. The 5-year survival rates range between 25% and 45%. Favorable prognostic factors include – solitary lesion, immunocompetent patient, absence of leptomeningeal or periventricular spread, and age less than 60 years. Long-term survivors are at risk of developing leukoencephalopathy (progressive dementia, ataxia, and urinary incontinence) as a side effect of radiation. If the tumor relapses, the site is CNS (most cases) or testis (small proportion of cases). The image shows primary high-grade B-cell lymphoma of the CNS. The tumor cells diffusely infiltrate through the brain parenchyma (same case as the previous slide).