“…10 ALK+ ALCL is associated with a better prognosis than ALK-ALCL, and the International Prognostic Index, originally proposed for non-Hodgkin lymphomas, is an effective tool to predict outcomes. 11 Although ALCL frequently involves lymph nodes and occasionally involves extranodal sites, it rarely occurs in the CNS, 12 and in the literature, ALCL of the CNS is limited to case reviews. [13][14][15][16][17][18] A few case reviews suggested that although ALK positivity and younger age appear to be favorable prognostic factors for primary ALCL of the CNS, it is generally much more aggressive than systemic ALCL or primary CNS lymphoma.…”