Primary central nervous system lymphoma: a clinicopathological study of 75 cases

Aims: Pathological and clinical data in a large series of immunocompetent patients with primary lymphoma of the central nervous system (PCNSL) were analysed. Methods: We immunostained tumour specimens of 75 patients for CD3, CD4, CD5, CD8, CD10, CD20, CD30, CD79a, Bcl-2, Bcl-6, CD138, MUM1, TDT, PAX5, FOXP1 and Ki-67 and performed in situ hybridisation for Epstein-Barr virus (EBV) RNA. Eleven cases were investigated for rearrangements of BCL6, immunoglobulin heavy chain (IGH) and FOXP1 genes using fluorescent in situ hybridisation (FISH). Results: Histologically, most cases were classified as diffuse large B-cell lymphoma (80.2%) predominantly of centroblastic type. Immunophenotypic profiling revealed that 96% and 4% of cases corresponded to non-germinal centre and germinal centre type, respectively. FISH analysis showed t(3; 14)/IGH-BCL6 in 2/11 cases and trisomy 3 in 2/11 cases. FOXP1 rearrangements were not found. At survival analysis, Karnofsky index > 80 and presence of Bcl-6 expression showed independent significant association with favourable patient outcome. Conclusions: PCNSL represents a histologically and immunophenotypically very homogeneous lymphoma type, probably derived from germinal centre exit B cells. The frequent overexpression of FOXP1 appears not to be related to FOXP1 gene rearrangement. Survival analyses disclosed Bcl-6 expression and high Karnofsky performance score as independent prognostic parameters associated with favourable outcome.