Multiple unrelated clones in myelodysplastic syndrome and in acute myeloid leukemia.

We identified cytogenetically unrelated clones in the bone marrow of 12 of 240 patients with myelodysplastic syndrome (MDS) and in 3 of 232 patients with acute myeloid leukemia (AML). In addition, unrelated single-cell abnormalities were found in six MDS and two AML patients. The most commonly encountered abnormalities present in the unrelated clones in patients with refractory anemia (RA) were del(5q), +8, and -7. In blastic types of MDS and AML trisomy 8 was found in two of eight patients while in the remaining cases the chromosome abnormalities were diverse and nonspecific. The presence of the chromosomally unrelated clones, together with recent data on the early appearance of monoclonality provided by molecular biology studies, support the interpretation that aberrations such as +8 and del(5q) are actually secondary abnormalities that develop during tumor progression in a cell with a primary submicroscopic genomic rearrangement.