″Minor″ BCL2 Breakpoints in Follicular Lymphoma

Abstract

Follicular lymphomas are frequently associated with the t(14;18)(q32;q21). This translocation can be detected by karyotype, polymerase chain reaction (PCR), and fluorescence in situ hybridization (FISH). In addition to the breakpoints currently used for diagnosis located in the major breakpoint region (MBR) and the minor cluster region (mcr), recent studies have reported the existence of other breakpoints (3′ BCL2, 5′mcr, and icr). In this study, we examined the frequency of all five breakpoints in 236 cases of follicular lymphomas by real-time PCR analysis. The distribution of breakpoint sites consisted of MBR in 118 cases (50%), mcr in 11 (5%), icr in 32 (13%), 3′ BCL2 in 13 (6%), and 5′ mcr in three cases (1%). These findings illustrate significantly higher frequency of the icr breakpoint as compared with the more frequently studied mcr. Correlation of breakpoints with histology showed that MBR breakpoints occur more frequently in grade 2 lymphomas (P = 0.042). A majority of the PCR-negative cases (75%) contained an IGH/BCL2 translocation with FISH methods, suggesting the presence of other BCL2 breakpoints. Correlation of breakpoints with survival did not reveal significant differences. Diagnostic laboratories should consider expanding their PCR methods to include other BCL2 breakpoints and correlating with FISH methods when appropriate.