Near-tetraploid clones in acute leukemia

Abstract

Near-tetraploid clones were observed in bone marrow (BM) samples from two patients with acute leukemia. One case had a hypotetraploid clone (modal chromosome range, 88-90) characterized by two apparently identical 8;21 translocations and loss of both Y chromosomes as well as by other changes. As in aneuploid patients with only a single 8;21 translocation, the cytologic features in this case were characteristic of acute myeloid leukemia with maturation. The marrow of the second patient contained immature leukemic blasts indicative of acute myeloid leukemia. The abnormal clone in this patient contained 93 chromosomes with an extra small marker. In this case we examined BM preparations that were made by several different cytogenetic methods: 'direct' and 24-hr culture (with or without methotrexate synchronization). We scanned 100 consecutive mitotic cells from each of the three preparations and found almost no variation in the incidence of abnormal metaphase cells. However, in this particular case, we noted some disparity between preparations with respect to the quality of diploid mitoses versus that of near-tetraploid mitoses. This finding is discussed with regard to bias in selecting metaphase cells for banding analysis in acute leukemia in general. In both of our patients there was a close correlation between the incidence of polyploid mitoses observed in cytogenetic preparations and the incidence of bizarre blast cells found in BM smears on the same data.