MYC, BCL2, and BCL6 rearrangements in primary central nervous system lymphoma of large B cell type

Primary central nervous system lymphoma (PCNSL) is a rare specific subtype of non-Hodgkin lymphoma limited to the brain, leptomeninges, spinal cord, or eyes without any systemic presentation and relapse which mostly takes place in CNS. In more than 95% of patients, it is of diffuse large B cell lymphoma (DLBCL) type. Categorizing PCNSL to germinal center cell like or activated B cell like, as we usually do for DLBCL NOS, may not be applicable for predicting outcome. Possible prognostic significance of MYC, BCL2, and/or BCL6 rearrangements may be important given what we know about their impact in systemic DLBCL, but we have limited knowledge about the status of double or triple hit molecular changes in PCNSL. Here, we have investigated prevalence of these molecular alterations in PCNSL. Two independent tissue microarrays constructed from 78 formalin-fixed paraffin-embedded blocks of confirmed PCNSL were tested for rearrangement of MYC, BCL2, and BCL6 by interphase fluorescent in situ hybridization (FISH) using break apart dual color probes. BCL6 translocation was detected in 15 (12%) cases. Translocation involving MYC and BCL2 was identified in 3 cases (3.8%) and 1 case (1.3%) respectively. One double hit lymphoma was discovered with both MYC/BCL2 translocation (1.3%). To the best of our knowledge, few organized studies have been conducted for MYC, BCL2, and/or BCL6 rearrangement in PCNSL. This study is evaluating large number of PCNSL. Double or triple hit events which are rarely seen in PCNSL.