Unusual relapse of primary central nervous system lymphoma at site of lumbar puncture

Primary CNS lymphoma (PCNSL) is a rare non-Hodgkin's lymphoma confined to the CNS. Local relapse of this disease is common, but extracranial or subcutaneous metastasis is rare with only a few cases being reported in literature. We report a 63-year-old male patient, who responded well to treatment for PCNSL but relapsed two and half years later with a lumbosacral nodule at the site of a previous lumbar puncture due to microscopic tumor seeding. Clinicians treating patients with PCNSL must remain alert to the possibility of extracranial solitary relapse even after the resolution of initial disease because prompt treatment can result in a good outcome.