Detection of the chromosomally abnormal clone in acute lymphoblastic leukemia

Bone marrow and peripheral blood from 121 children with acute lymphoblastic leukemia spent 3 hours in transit before being cultured. Cultures were harvested directly, after 24, 48, or 72 hours, and following methotrexate synchronization. Details of techniques are given. Analyzable mitoses were obtained in 78 cases. Failures contained no detectable clone and fewer than five mitoses (27 cases) or fewer than five analyzable mitoses (16 cases). A clone was found in 44 cases. In some cases the clone was found in two or more cultures, conversely a clone in the direct harvest was not always found after overnight culture and vice versa. Hyperdiploid clones were always found in the bone marrow and frequently in two or more cultures. Pseudodiploid clones found in the blood in four cases evaded detection in the bone marrow. The use of methotrexate did not yield prometaphase chromosomes or improve the yield of analyzable cells. The number of cultures employed influenced the yield of metaphases and appeared to influence clone detection. More cultures were needed to detect a pseudodiploid clone than to detect a hyperdiploid clone. Detection of a clone may be maximized by using the following combination of cultures: bone marrow direct and overnight, and peripheral blood overnight.