This patient has a previous history of a systemic B cell lymphoma treated with chemotherapy. After biopsy confirmation of the cerebellar lesion, the patient was referred back to his hematologist for further systemic investigation and treatment. 

Secondary CNS lymphoma is typically a non-Hodgkin lymphoma and, unlike primary CNS lymphoma it more commonly involves the leptomeninges and is uncommonly detectable on CT/MR, with malignant cells found of CSF aspiration.