The Grey Zone between Burkitt and Diffuse Large B Cell Lymphomas: Impact of Chromosomal Breakponts at Myc and Other Loci.

A prompt distinction of Burkitt lymphoma (BL) versus diffuse large B cell lymphoma (DLBCL) has important clinical implications. We analyzed 74 adult grey zone lymphomas (BL/DLBCL) and 10 reference pediatric BL using immunohistochemistry for Ki-67, CD10, bcl2 and bcl6, and Fluorescence In Situ Hybridization (FISH) for MYC, BCL2 and BCL6 breakpoints. Four hematopathologists reached a final (consensus) diagnosis independently in 80% of the reference BL, 24% of the test BL and 69% of the DLBCL. A MYC breakpoint was detected in all reference BL, 95% of the test BL and 35% of the DLBCL. BCL2 and BCL6 breakpoints were infrequent in BL (5 and 6%) and DLBCL (13% and 16%). Three BL and 5 DLBCL contained double breakpoints. A phenotypic shift to BL in the DLBCL group was indicated by the expression of CD10 and bcl6 in 67% and 91% of the cases, respectively. One third of all lymphomas showed a classical genotype and expression pattern of BL (MYC breakpoint+, Ki-67>90%, CD10+, bcl6+, bcl2-) but only 63% of these cases were classified as BL. Our data indicate that a subgroup of DLBCL shares markers with BL, which is probably due to an overlapping histogenesis of both tumors.

Value of immunohistochemistry and additional FISH for BCL2 and BCL6 breakpoints to reach the consensus diagnosis in 38 MYC breakpoint carrying cases of adult grey zone BL / DLBCL lymphomas