Light scatter characteristics of blast cells in acute myeloid leukaemia: association with morphology and immunophenotype.

AIMS: To analyse the forward scatter/side scatter (FSC/SSC) distribution of acute myeloblastic leukaemia (AML) blast cells in order to assess whether it correlates with their morphology, immunophenotype, and clinical and biological disease characteristics. METHODS: FSC/SSC patterns were established upon taking into account the localisation of the residual T lymphocytes in the FSC/SSC dot plot as an internal biological standard. One hundred and seventy one newly diagnosed AML patients were analysed and five different FSC/SSC patterns were established. These five patterns could be grouped into two major categories taking into account the FSC/SSC distribution of normal cells in a bone marrow aspirate: immature patterns (1 and 2) and mature patterns (3, 4, and 5). These FSC/SSC patterns were correlated with different clinical and biological characteristics of AML patients. RESULTS: No significant associations were detected in relation to the clinical and haematological disease characteristics and the prognosis of these patients. By contrast there was a significant correlation between the FSC/SSC pattern of the AML blast cells and the FAB classification. An increased reactivity for the antigens associated with myeloid differentiation such as CD13, CD33, CD11b, CD15, CD14, CD4, CD56, and/or CD16 was detected among cases showing a mature FSC/SSC pattern (3, 4, and 5), both in the whole series and even within each of the FAB AML subtypes. By contrast, the reactivity for the CD34 precursor cell associated antigen was higher among those cases displaying an immature FSC/SSC pattern, this being observed even within each FAB subgroup. CONCLUSIONS: The FSC/SSC pattern distribution of AML blast cells not only provides an additional objective and reproductible system for the classification of these leukaemias but it may also represent a connection between the FAB morphological groups and the immunophenotypic classification of AML patients.

DNA aneuploidy in acute myeloblastic leukemia is associated with a high expression of lymphoid markers.

In the present study the DNA cell content of 205 de novo acute myeloblastic leukemia (AML) patients is analyzed at flow cytometry in order to determine both the incidence of DNA aneuploidy in AML patients and the clinical and biological characteristics of AML aneuploid cases. All technical procedures were performed in accordance with the proposed guidelines of the DNA Cytometric Consensus Conference. Our results show that the incidence of DNA aneuploidy is quite low (4.8%), with most cases (n = 8) hyperdiploid and only a small proportion (n = 2) hypodiploid. No major differences were detected between the aneuploid and diploid cases with respect to the clinical and prognostic disease characteristics. Regarding the immunophenotype of the blast cells, the aneuploid cases displayed both a higher incidence of immature myeloblastic phenotype and a greater expression of lymphoid-associated antigens. In summary, our results show that AML patients display a quite low incidence of DNA aneuploidy and that despite the fact that these cases do not display particular clinical characteristics, they show an association with the expression of lymphoid-related markers.

Prognostic value of S-phase cells in AML patients.

Until now, reports on the cell cycle distribution of AML patients have shown highly variable results which are probably related to the technical heterogeneity of such studies. The aim of the present paper was to analyse in 204 AML patients at diagnosis the proliferative rate (assessed by the number of S-phase cells) of peripheral blood (PB) (126 cases) and bone marrow (BM) (78 cases) cells in order to explore its relationship with disease characteristics. A strong parallelism was observed regarding the relationship between the proliferative rate of the blast cells both in PB and in BM and the disease characteristics. Cases with a high proliferative rate were associated with advanced age, high WBC counts and LDH serum levels, monocytic leukaemias (assessed both by morphological and immunophenotypic criteria) and NK-associated antigens (CD56, CD16). The proliferative activity did not influence the CR rate; in contrast, cases with a high number of S-phase cells had shorter survival. In addition, multivariate analysis showed that age, the expression of CD11b, and the S-phase counts are the only three prognostic factors displaying an independent impact on survival.