The incidence of primary central nervous system lymphoma (PCNSL) has increased during the past 40 years. This has been associated with immunodeficiency, mainly in patients infected with the human immunodeficiency virus (HIV) and in transplant patients. Tumor genesis is related with the Epstein-Barr virus (EBV). The most frequent PCNSL immunophenotype is B-cell lymphoma. Clinical manifestations depend on tumor localization, and are usually behavior dysfunctions and intracranial hypertension syndrome. Differential diagnosis must take into consideration infectious processes, stroke, primary brain tumors, and metastases. The diagnosis of PCNSL requires brain MRI and brain biopsy. It is important to assess HIV infection when diagnosing PCNSL. This review reports a case of primary brain lymphoma in a patient who underwent renal transplantation due to polycystic kidney disease 8 years before.