DETECTION OF CBF-BETA MYH11 FUSION TRANSCRIPTS IN ACUTE MYELOID-LEUKEMIA - HETEROGENEITY OF CYTOLOGICAL AND MOLECULAR CHARACTERISTICS/

Pericentric inversion of chromosome 16, translocation (16;16) and del( 16q), resulting in a chimerical fusion of CBF beta and MYH11 genes, ar e typically seen in the M4Eo French-American-British (FAB) classificat ion subset of acute myelogenous leukemia (AML). In this study, ww anal yzed 70 cases of acute non-lymphoblastic leukemia, mainly of the M4 or M5 type. We report the very unusual presence of the t(16;16) and CBF beta/MYH11 fusion transcript in an M7 patient. Ten M4Eo and four non-M 4Eo patients presented an inv(18), t(16;16) or CBF beta/MYH11 fusion t ranscript. Int most cases, the common 'A-type' CBF beta/MYH11 fusion t ranscript was detected. In addition to the eight different breakpoints and the three alternative splicing variants already described, eviden ce of a new CBF beta/MYH11 fusion transcript was found which involves a 785-bp deletion of MYH11. Moreover, two patients had an unusual tran script, to our knowledge only observed once. Only one patient had abno rmal eosinophilic differentiation without chromosome 16 cytogenetic ab normalities or detectable CBF beta/MYH11 fusion. Conversely, only one patient presented CBF beta/MYH11 fusion without abnormal eosinophilic differentiation. Altogether, our data suggest a correlation between th e CBF beta/MYH11 fusion transcript and characteristic abnormal eosinop hilic differentiation, whatever the PAC subtype or the percentage of a bnormal eosinophils.