Phenotyping of malignant hematopoietic cells. Analysis of 1200 cases of leukemia-lymphoma

Acute biphenotypic leukaemia: immunophenotypic and cytogenetic analysis

The incidence of acute biphenotypic leukaemia has ranged from less than 1% to almost 50% in various reports in the literature. This wide variability may be attributed to a number of reasons including lack of consistent diagnostic criteria, use of various panels of antibodies, and the failure to recognize the lack of lineage specificity of some of the antibodies used. The morphology, cytochemistry, immunophenotype and cytogenetics of acute biphenotypic leukaemias from our institution were studied. The diagnostic criteria took into consideration the morphology of the analysed cells, light scatter characteristics, and evaluation of antibody fluorescence histograms in determining whether the aberrant marker expression was arising from leukaemic blasts or differentiated bone marrow elements. Fifty-two of 746 cases (7%) fulfilled our criteria for acute biphenotypic leukaemias. These included 30 cases of acute lymphoblastic leukaemia (ALL) expressing myeloid antigens, 21 cases of acute myelogenous leukaemia (AML) expressing lymphoid markers, and one case of ALL expressing both B- and T-cell associated antigens. The acute biphenotypic leukaemia cases consisted of four major immunophenotypic subgroups: CD2+ AML (11), CD19+ AML (8), CD13 and/or CD33+ ALL (24), CD11b+ ALL (5) and others (4). Chromosomal analysis was carried out in 42/52 of the acute biphenotypic leukaemia cases; a clonal abnormality was found in 31 of these 42 cases. This study highlights the problems encountered in the diagnosis of acute biphenotypic leukaemia, some of which may be responsible for the wide variation in the reported incidence of this leukaemia. We suggest that the use of strict, uniform diagnostic criteria may help in establishing a more consistent approach towards diagnosis of this leukaemic entity. We also suggest that biphenotypic leukaemia is comprised of biologically different groups of leukaemia based on immunophenotypic and cytogenetic findings.

Immunophenotyping of acute myeloid leukaemia: relevance of analysing different lineage-associated markers

The immunophenotype of 135 previously untreated patients with FAB defined acute myeloid leukaemia (AML) was studied at diagnosis. The panel of reagents included monoclonal antibodies (MoAb) recognising myeloid-associated determinants (CD11, CD13, CD14, CD33 and others) as well as MoAb directed towards lymphoid antigens (CD7, CD10, CD19) and TdT. The results indicate that CD13 and/or CD33 are consistently expressed in AML and only rarely in ALL blasts (131/135 + ve cases, versus 4/130 in ALL). Lymphoid antigen expression was rarely detected when CD10 and CD19 were investigated in AML (0.9% and 2% + ve cases, respectively), whereas significant positivities were found for TdT and CD7 (20% and 10% respectively). Concerning FAB subtypes, two new MoAb (LAM3 and LAM7) proved very useful in the specific recognition of AML with monocytic features. The phenotype CD13+ and/or CD33+, CD9+, HLA-DR- was found to be almost exclusive for M3 AML. The response to induction chemotherapy was analysed in CD7+ and in TdT+ patients. In the latter group a statistically significant lower response rate was found with respect to TdT-ve-AML patients.

Occurrence of particular isoenzymes in fresh and cultured leukemia-lymphoma cells. III. Esterase isoenzyme in monocytes

The expression of a particular alpha-naphthyl acetate esterase isoenzyme which is specific for monocytes was examined in a panel of cultured leukemia-lymphoma cell lines (n = 88), freshly obtained leukemia-lymphoma cells (n = 527), and in fresh (n = 10) and cultured (n = 22) leukemia cells treated with the phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA). The sodium fluoride-sensitive isoenzyme was separated by isoelectric focusing on horizontal thin-layer polyacrylamide gels. The esterase isoenzyme was not detected in untreated or TPA-treated lymphoid, erythroid, or Hodgkin's disease-derived cell lines, but was seen in leukemia cell lines of monocytic origin. TPA induced the new expression of this marker isoenzyme in two leukemia cell lines of promyelocytic and erythroid origin that are known to differentiate along the monocytic-macrophage cell lineage; TPA stimulation increased the staining intensity of the band in monocytoid cell lines. This esterase isoenzyme was found in 92% of the cases classified morphologically as acute myelomonocytic or monocytic leukemia, but only in 3% of the non-monocytic acute myeloid leukemias. All lymphoid or erythroid leukemias or lymphomas were negative. Treatment with TPA of AML and CML cells, which commonly differentiate to monocyte/macrophage-like cells, showed de novo the monocyte-specific isoenzyme. It is concluded that this isoenzyme is a characteristic marker for monocytic leukemia cells and will be a useful tool for the discriminatory identification of the monocytic element in normal and leukemic cells.