c-myc overexpression is not mandatory in aggressive-phase multiple myeloma with Burkitt's type translocation

This report concerns a case of aggressive-phase multiple myeloma (AGMM) with Burkitt's type translocation t(8;14)(q24;q32), detected by Giemsa-banding. Double-color fluorescence in situ hybridization identified the breakpoint on 8q24 at a comparatively centromeric site, which was at least 300 kb and possibly 600 kb distant from the c-myc coding region. The breakpoint on 8q24 of the present case was far removed from that seen in other B-cell neoplasms with t(8;14)(q24;q32). Despite the presence of t(8;14)(q24;q32), neither rearrangement nor overexpression of the c-myc gene was observed in this case. Although our case may be a special case of multiple myeloma, it nevertheless suggests that overexpression of c-myc is not mandatory in an AGMM patient with Burkitt's type translocation. t(8;14)(q24;q32) which was seen in our case represents one of the first to be mapped at more than 300 kb 5' of c-myc. It should also be noted that this result could mean that a centromeric boundary 5' of c-myc exists where the influence of the immunoglobulin (Ig) H enhancer on c-myc transcription is not effective.