Cytogenetic analysis of different cellular populations in chronic myelomonocytic leukemia.

Karyotypes of different cellular populations made after separation of bone marrow cells on a gradient of Percoll were evaluated in seven patients affected by chronic myelomonocytic leukemia diagnosed according to FAB criteria. Megakaryocytes, monocytic cells, and granulocytic and erythroid precursors were preferentially collected after centrifugation between density layers of 1045-1050 mg/ml, 1050-1060 mg/ml, and 1065-1070 mg/ml, respectively. The enriched cell fractions were cultured separately and submitted to cytogenetic investigation after short-term culture. Some chromosome aberrations (5q-,+8) were observed in all cellular fractions in three patients, thus providing cytogenetic evidence of the involvement of a common progenitor stem cell in this myelodysplastic disorder. On the other hand, chromosome abnormalities such as del(3)(q21) and del(11)(q23) appeared to be confined to the megakaryocytic and the monocytic fractions, respectively, in two patients. It is conceivable that lineage-restricted aberrations may develop as a consequence of a multistep clonal evolution and may show a close relationship with the hemopoietic differentiative processes.