MULTIPLE UNRELATED CLONES IN MYELODYSPLASTIC SYNDROME AND IN ACUTE MYELOID-LEUKEMIA

We identified cytogenetically unrelated clones in the bone marrow of 1 2 of 240 patients with myelodysplastic syndrome (MDS) and in 3 of 232 patients with acute myeloid leukemia (AML). In addition, unrelated sin gle-cell abnormalities were found in six MDS and two AML patients. The most commonly encountered abnormalities present in the unrelated clon es in patients with refractory anemia (RA) were del(5q), +8, and -7. I n blastic types of MDS and AML trisomy 8 was found in two of eight pat ients while in the remaining cases the chromosome abnormalities were d iverse and nonspecific. The presence of the chromosomally unrelated cl ones, together with recent data on the early appearance of monoclonali ty provided by molecular biology studies, support the interpretation t hat aberrations such as +8 and del(5q) are actually secondary abnormal ities that develop during tumor progression in a cell with a primary s ubmicroscopic genomic rearrangement.