A systematic analysis of the blast cell population was carried out on samples from 50 patients suffering from blast transformation of chronic granulocytic leukaemia (CGL) (31) and of myelofibrosis (4), acute myelofibrosis (AM) (11) and undifferentiated acute leukaemia (4). Transmission electron microscopy (TEM), used in 41 samples, included: morphology and techniques for myeloperoxidase (MPO), platelet-peroxidase (PPO) and acid phosphatase (AP). The majority of cases were also studied by light microscopy cytochemistry and with a battery of cell markers which are reported in the accompanying paper (San Miguel et al, 1985). The characterization of the type(s) of proliferating blasts was made from the integration of ultrastructural and immunological data. TEM morphology allowed the precise recognition of specific granules in basophil and mast-cell precursors and of ferritin particles in blasts of erythroid lineage; these rare cell types were not adequately characterized by other methods. The PPO reaction made possible the identification of pure megakaryoblastic proliferations in 38% of cases, including eight of the 11 with AM; megakaryoblasts were also present in nine of 12 cases with mixed blast cell types. The MPO and AP reactions were useful for the characterization of myeloblasts and monoblasts, respectively. Lymphoblasts could be distinguished from other cell types by TEM morphology and negative MPO and PPO reactions. TEM techniques were valuable for diagnosing correctly the type of blast cell in this study in which only four cases (8%) remained unclassifiable.
A panel of 19 monoclonal antibodies (McAb) and the enzyme terminal transferase (TdT) have been applied to the characterization of poorly differentiated blasts from 50 patients with chronic granulocytic leukaemia (CGL) and myelofibrosis in blast crisis (BC), acute myelofibrosis and undifferentiated leukaemia. These cells were also extensively studied by transmission electron microscopy (TEM) (see Polli et al, 1985a). McAb against platelet glycoproteins (GP) showed a high specificity for megakaryoblasts, in particular those reactive with the GPIIb/IIIa complex (J15) and GPIIIa (C15 and C17), which were positive in a higher proportion of blasts than the McAb to GPIb (AN51 and FMC25). Findings with these anti-platelet McAb paralleled those of the platelet-peroxidase (PPO) reaction in 76% of cases studied simultaneously. The PPO reaction was always positive in cases in which two or more of the McAb were reactive with the blast cells. The differences observed suggest, nevertheless, that PPO is more sensitive for megakaryoblasts than the McAb and that this TEM technique should be reserved for cases which are negative with the platelet specific McAb. Of the McAb against myeloid antigens used in this series OKM1 was positive in 50% of cases but the others failed to demonstrate early features of differentiation in myeloblasts and monoblasts. In only three cases were erythroid precursors demonstrated by TEM and these were the only ones reactive with a McAb to glycophorin-A (LICR LON/R10). TdT and the McAb J5 helped in the identification of lymphoblasts which were seen as a 'pure' proliferation in 23% of CGL-BC and as part of blast cell mixtures in another 17% of cases. The McAb reactive to haemopoietic precursor cells (RFB1, FMC8 and OKIa), on the other hand, were of no practical value for the classification of blast cell types. The lineage specificity of several of the McAb used in this study, confirmed by TEM, suggest that these reagents are valuable tools for the characterization of immature blast cells.
A cytogenetic analysis was carried out on bone marrow cells from 11 patients who presented with hypereosinophilia and the clinical features of the idiopathic hypereosinophilic syndrome. One of these patients was found to have trisomy 8 affecting the myeloid series, including eosinophils. In this patient, marrow eosinophils also showed asynchrony of nuclear-cytoplasmic maturation, and there were increased numbers of myeloid progenitor cells in the blood. Six months later, blast cell transformation occurred, and he died soon afterwards. These findings show that abnormalities in the karyotype of bone marrow cells and culture of blood progenitor cells may help to identity eosinophilic leukaemia among patients who present with features of the idiopathic hypereosinophilic syndrome.
The authors report a patient with Ph1-positive chronic granulocytic leukemia (CGL) who developed "blast crisis" after six years of chronic phase. The presence of mast cell precursors and basophil blasts was demonstrated by ultrastructural morphology and cytochemistry. Membrane phenotype studies with monoclonal antibodies helped in the further characterization of these cells. The possible implication of these findings in the origin of mast cells and the relationship of these cells with basophils are discussed.
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