[A 36-year-old woman with primary central nervous system lymphoma diagnosed by twice brain biopsies, showing relapsing and remitting brain lesions].

A 36-year-old woman visited a local hospital suffering from acute onset dizziness. Brain MRI revealed multiple white matter lesions without gadolinium enhancement in the both hemispheres. Although she began to receive a treatment under a clinical diagnosis of multiple sclerosis, she developed newly emerging brain lesions and was referred to our hospital. Neurological examination detected intention tremor, right-sided dysdiadochokinesis, and gait ataxia. Both blood and cerebrospinal fluid tests were unremarkable but follow-up brain MRIs showed rapidly relapsing and remitting lesions. The first brain biopsy ended up showing non-specific changes but the second biopsy with five months interval confirmed primary central nervous system lymphoma (PCNSL). The patient was treated by chemotherapy and showed partial response. It is important to consider sequential brain biopsies if needed because PCNSL may present diverse brain lesions on MRI including non-neoplastic early lesions.