A 49-year-old right-handed woman presented with a 3-week history of progressive ataxia, dysarthria, right hemiparesis, cognitive decline, and headache. Infectious, inflammatory, neoplastic, and paraneoplastic workup results were unremarkable. The ophthalmologic evaluation findings were unremarkable for inflammatory or neoplastic involvement. Repeated lumbar puncture findings revealed mild lymphocytic pleocytosis with mildly elevated proteins. Cerebrospinal fluid cytology and flow cytometry results were negative. Magnetic resonance imaging of the brain showed a diffusely enhancing lesion typical for CLIPPERS (chronic lymphocytic inflammation with pontine perivascular enhancement responsive to steroids).1 Biopsy was felt to be risky given the deep location of the lesion, hence the patient was treated with steroids. The patient showed moderate clinical improvement initially and there was significant reduction in edema on magnetic resonance imaging but persistent perivascular curvilinear enhancement (Figure 1 and Figure 2). With subsequent clinical progression while the patient was taking steroids, a cerebellar biopsy was performed and revealed primary large B-cell non-Hodgkin lymphoma (Figure 3). The patient underwent 4 cycles of high-dose methotrexate, rituximab, and temozolomide. Following the first 2 cycles, she had a complete resolution of her speech symptoms and significant improvement of her right-sided weakness. Unfortunately, her treatment was complicated by steroid-induced diabetes mellitus, bilateral avascular necrosis of the hips and right shoulder, and septic right hip arthritis, which resulted in deconditioning and generalized weakness. Magnetic resonance imaging at 6 months showed complete resolution of abnormal enhancement and near-complete resolution of her abnormal T2–fluid-attenuated inversion recovery hyperintense signal abnormality, and the patient was considered to be in remission.