Primary CNS Anaplastic Large Cell Lymphoma DUPS22 Rearranged with Gain of ALK: A Case Report and Review of the Literature

ALK‐negative anaplastic large cell lymphoma (ALCL) is a rare primary central nervous system lymphoma (PCNSL). Although DUSP22 rearrangement is considered favorable in systemic ALK‐negative ALCL, survival remains poor in PCNSL. We report a case of PCNSL ALK‐negative ALCL with DUSP22‐IRF4 rearrangement and an unusual gain of the ALK gene (2p23), complicated by transaminitis, treated with high‐dose methotrexate followed by whole‐brain radiation therapy, achieving durable remission exceeding 3 years. To our knowledge, this is the first reported case in the CNS setting, suggesting that DUSP22 rearrangement and ALK gain may confer a favorable prognosis. Trial Registration The authors have confirmed clinical trial registration is not needed for this submission.