A direct bone marrow chromosome technique for acute lymphoblastic leukemia

We describe a direct bone marrow chromosome technique that was developed especially for use in studies of acute lymphoblastic leukemia (ALL). The features responsible for technical improvements include: the use of RPMI 1640 medium, supplemented with 30% fetal calf serum, to support cellular activity during both specimen transport and Colcemid treatment; the processing of only 0.1 ml of sedimented cells or less per centrifuge tube; the exposure of cells to Colcemid for a maximum of 25 min; control of the total time of exposure to hypotonic solution; the use of a steel wire as a stirring rod (fashioned to fit the centrifuge tube) for mixing cells; slide preparation by a specific edging-flaming technique; the natural aging of the slides to achieve optimal drying; and the use of a modified G-banding procedure that employs Wright's stain. This technique has been used in more than 350 cases of ALL and has consistently provided analyzable banded chromosomes, even in hyperdiploid cases with up to 91 chromosomes. It makes the previously recognized morphological difference between metaphases of residual normal cells and those from the leukemic clone less apparent. The edging-flaming technique of slide preparation is the most important component and is especially appropriate for spreading large numbers of chromosomes in ALL.