GENE REARRANGEMENT IN ACUTE NONLYMPHOBLASTIC LEUKEMIA - CORRELATION WITH MORPHOLOGICAL AND IMMUNOPHENOTYPIC CHARACTERISTICS OF BLAST CELLS

The presence of Ig and TCR gene rearrangement has been reported to occur in ANLL. However, most of the studies have been performed in short series of patients and, in general, not all rearranging genes have been included. We have investigated the configuration of immunoglobulin (Ig) and T-cell receptor loci (TCR) in a series of 160 untreated patients with de novo acute non-lymphoblastic leukaemia (ANLL) and correlated the results with the morphological and immunophenotypic characteristics of blast cells. IGH gene rearrangement was detected in 16/160 cases analysed (10%) and IGK was rearranged in half of them. The incidence of cases displaying TCRB, TCRG and TCRD rearrangements was 5.6%, 13.8% and 13%, respectively. Concomitant recombinatorial events including different Ig and/or TCR genes were frequently detected. Gene rearrangement was not related to the stage of cell differentiation within the myeloid lineage assessed both by morphological and immunophenotypic criteria. Regarding the correlation with the presence of lymphoid related markers, the only relevant association was between the expression of CD7 antigen and TCRG and TCRD gene rearrangement. Our results show that the incidence of gene rearrangement in ANLL may be slightly higher than previously suspected, and that it is not associated with early stages of cell differentiation nor to the expression of lymphoid markers.