Introduction
Primary Central Nervous System Lymphoma (PCNSL) is an extranodal non-Hodgkin lymphoma (NHL) originating in brain tissue, spinal cord, leptomeninges and vitreoretinal eye accounting for 3% to 5% of all brain tumors and less than 1% of all NHLs. The 95% of PCNSLs are B-cell lymphomas; T-cell lymphomas constitute the remaining 2-5%1. Pediatric PCNSLs are very rare (about 1%). Cerebral hemisphere, basal ganglia, corpus callosum, brainstem and cerebellum are the most common involved brain sites. Clinical manifestations include headache, aphasia, sensory and motor deficits, speech disorders, ataxia, seizures and short- term memory difficulties2. ALCL is a peripheral T-cell lymphoma, accounting for about 2-8% of all NHLs. Brain ALCL is a very rare subtype of PCNSL. Mean age at diagnosis is 21 years and leptomeningeal involvement occurs in 80% of cases as tan-white nodules on the dural surface3. ALCL can be classified into ALK+ and ALK- ALCL, according to the pattern of genetic abnormalities. ALK+ cases generally occur in younger patients and have a more favorable prognosis than ALK- cases, with two years survival rate of 71% and 22% respectively3. ALCLs are hypointense on MRI T1 and isointense to hyperintense on T2-weighted images, mainly occurring as single or multiple supratentorial lesions. The enhancement pattern doesn’t clearly distinguish it from meningiomas, metastasis or gliomas4.