Multiple chromosomally distinct cell populations in myelodysplastic syndromes and their possible significance in the evolution of the disease.

Serial chromosome investigations performed in untreated myelodysplastic syndromes (MDS) revealed that: multiple chromosomally unrelated cell populations may emerge during the course of the disease; chromosome changes of the clonal type may disappear or become undetectable, and may or may not reappear during further evolution. The former of these phenomena was found in four cases and was consistently associated with clinical-haematological progression of the disease to a more malignant form, including acute leukaemia. The second was apparently unrelated to clinical and haematological changes in the evolution pattern. These observations are in favour of the hypothesis that MDS evolve as a multistep process in which several events, including the acquisition of sometimes unrelated chromosome changes determine the progression of the disease.