Clinicopathologic features of primary central nervous system anaplastic large cell lymphoma: a multicenter study identifies age and ALK status as prognostic factors.

Anaplastic large cell lymphoma with primary presentation in, and disease limited to, the central nervous system (primary CNS ALCL) is a rare and aggressive lymphoma found in a sensitive anatomic site. We report the clinical and pathologic characteristics of 17 primary CNS ALCL cases that are newly reported from six academic medical centers. We are investigating the characteristics of these cases, alongside their commonalities and differences from systemic ALCL arising at conventional anatomic sites. Clinical, pathologic, and outcome data were extracted by medical record review. The median patient age was 32 years with a male-to-female ratio of 2.4:1. Cases presented with either localized or multifocal central nervous system (CNS) disease without coinciding systemic disease. Histologically, the common pattern prevailed, and loss of pan-T-cell markers was frequent. There was a similar proportion of anaplastic lymphoma kinase (ALK) positivity in primary CNS ALCL (12/17, 71%) compared to that reported in systemic ALCL (70-80%). Our data indicate a 5-year overall survival (OS) rate of 65% and a 5-year progression-free survival (PFS) rate of 48%. Five patient deaths occurred in this study of which all were in the ALK-negative group, and all were patients over 40 years old. ALK-positive patients were significantly younger than ALK-negative patients, and survival analyses showed that both ALK-positive and younger age (≤ 40 years) were favorable prognostic factors. This is the largest series of primary CNS ALCL reported to date, which demonstrates a high proportion of ALK-positive cases and favorable outcomes for both younger and ALK-positive patients despite the involvement of a sensitive anatomic site.