Cytogenetic Studies in Myeloproliferative Disorders during Transformation into Leukaemia

Serial chromosome studies on bone marrow cells were performed in two patients with myeloproliferative disorders, in one of whom a transformation into leukaemia occurred. An increasing number of metaphases belonging to abnormal stem lines was seen in both cases. In one of the patients a clonal evolution was observed. The cytogenetic and cytologic findings in the bone marrow aspirates indicate that the chromosome abnormalities are present in the erythroblasts as well as in the white cell series and that the abnormal tem line does not occur secondary to the blastic transformation of the bone marrow in leukaemia. It is concluded that abnormal stem lines in patients with myeloproliferative disorders may express a neoplastic clone of cells.