Childhood biphenotypic leukemia: detection of mixed lymphoid and myeloid populations in bone marrow specimens

Acute bilineal leukemia: a rare disease with poor outcome

Most cases of acute leukemia can be assigned to the myeloid, B or T lineage. In a few cases, definitive assignment cannot be achieved because blasts express antigens of more than one lineage. A subset of these, referred to as acute bilineal leukemias (aBLLs), is characterized by the presence of more than one population of blasts, each comprising a single lineage. We identified 19 cases of aBLL, including 10 mixed T and myeloid (T-My) and nine mixed B and myeloid (B-My); no mixed B and T cases were identified. Cytogenetic data were available for 16 patients. Three of seven patients with B-My had a t(9;22)(q34q11.2), two had 11q23 translocations and one had del(9). Two of nine patients with T-My had 2p13 translocations; five had other unrelated abnormalities. Of 16 patients with outcome data, only six achieved complete remission and only two remain free of disease 2.5 and 4.5 years after chemotherapy or stem cell transplantation. aBLL is a rare disease that combines B or T and myeloid blasts. Cytogenetic abnormalities of t(9;22) and 11q23 are common in, and may be restricted to, B-My cases, while T-My cases have frequent but generally non-recurring abnormalities. Both types of aBLL are associated with poor outcome.

Cytogenetics, molecular and ultrastructural characteristics of biphenotypic acute leukemia identified by the EGIL scoring system

Biphenotypic acute leukemia (BAL) is a rare, difficult to diagnose entity. Its identification is important for risk stratification in acute leukemia (AL). The scoring proposal of the European Group for the Classification of Acute Leukemia (EGIL) is useful for this purpose, but its performance against objective benchmarks is unclear. Using the EGIL system, we identified 23 (3.4%) BAL from among 676 newly diagnosed AL patients. Mixed, small and large blast cells predominated, with FAB M2 and L1 constituting the majority. All patients were positive for myeloid (M) markers and either B cell (B) (17 or 74%) or T cell (T) (8 or 34%) markers with two exceptional patients demonstrating trilineage phenotype. Six (50%) of studied M-B cases were positive for both IGH and TCR. In six (26%) patients myeloid lineage commitment was also demonstrable by electron cytochemistry. Abnormal findings were present in 19 (83%) patients by cytogenetics/FISH/molecular analysis as follows: t(9;22) (17%); MLL gene rearrangement (26%); deletion(6q) (13%); 12p11.2 (9%); numerical abnormalities (13%), and three (13%) new, previously unreported translocations t(X;6)(p22.3;q21); t(2;6)(q37;p21.3); and t(8;14)(p21;q32). In conclusion, the EGIL criteria for BAL appear robust when compared against molecular techniques that, if applied routinely, could aid in detecting BAL and help in risk stratification.

Characterization of genetic instability in radiation- and benzene-induced murine acute leukemia

This study, using the CBA/Ca mouse as a model, compares genetic lesions associated with radiation- and benzene-induced acute leukemias. Specific types of leukemia included in the analyses are radiation-induced acute myeloid leukemia (ML), and benzene-induced lymphoblastic leukemias, lymphomas, or mix-lineage leukemias. These leukemias have histopathological characteristics similar to those seen in human acute leukemias. G-band cytogenetic analysis showed that specific deletions involving regions D-E of one copy of mouse chromosome 2 [del(2)(D-E)] were frequently associated in both radiation- and benzene-induced acute leukemias. In addition, translocations of chr2(D-E) were also observed in some cases. These results suggest an important role of chr2 (D-E) deletions and translocations in the development of radiation- and benzene-induced murine acute leukemias. Fluorescence in situ hybridization with DNA probes specific for 2(D-E), constructed in our laboratory by means of chromosomal microdissection and PCR amplification, also demonstrate 2(D-E) deletions and/or translocations in these leukemic cells. Aneuploidy of chromosomes 3, 15, 16, and Y were also frequently detected in benzene-induced leukemic cells with or without lesions on chr2. These cytogenetic findings support the previous observations that metabolites of benzene lead to spindle-fiber disruption or abnormal cytokinesis in exposed animals. In summary, genetic instabilities observed in leukemic cells isolated from mice that had developed leukemia after exposure to radiation or benzene are syntenic with those frequently detected in patients with myelodysplastic syndrome, acute ML, and acute lymphoblastic leukemia. Thus, the CBA/Ca mouse has several characteristics that make it an excellent model for the study of radiation or benzene leukemogenesis in humans.

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.

Predominant expression of lambda light chain in adult cases with non-T-cell acute lymphocytic and chronic myelogenous leukemia in lymphoid blast crisis

The authors investigated cytoplasmic immunoglobulins of the leukemic cells from 20 adult cases with non-T-cell acute lymphocytic leukemia (ALL) and from three cases with chronic myelogenous leukemia in lymphoid blast crisis using immunoelectron microscopy. They also studied these cases using various monoclonal antibodies. Of the 23 examined cases, nine were negative for both heavy and light chains of immunoglobulins; the authors defined these as common ALL. Two cases were positive for the mu chain but were negative for light chains; the authors defined these as pre-B-cell ALL. The remaining 12 cases were positive for either kappa or lambda light chains; these were defined as B-cell ALL. Of the 12 cases positive for light chains, 11 were positive for the lambda chain. Seven cases of the 11 positive cases for the lambda chain were negative for heavy chains. Eleven cases were positive either for both My4 and My9 or for one of the two antibodies. From these results, the authors conclude the following: (1) the ratio of pre-B-cell ALL among non-T-cell ALL cases (two of 23 cases) was lower in adults than in children; (2) of the light chain-positive cases, the lambda light chain-positive cases predominated (11 of 12 cases); (3) heavy chain-negative, lambda chain-positive cases (seven cases) were observed; and (4) one half of the leukemia cases showed dual phenotypes of B-cell and myeloid cell lineages.

Acute myeloid leukemia: immunohistologic findings in paraffin-embedded bone marrow biopsy specimens

Immunohistochemical investigations were performed on decalcified, paraffin-embedded iliac crest trephine biopsy specimens from 30 cases of acute myeloid leukemia (AML, as defined by the FAB classification) with antibodies against B cells (L26, 4KB5, MB1, Ki-B3), T cells (UCHL1, MT1), myeloid/histiocytic cells (anti-neutrophil elastase, MAC387, anti-S-100 protein, anti-alpha 1-antichymotrypsin, DAKO-M1), natural killer/killer cells (anti-Leu-7), and megakaryocytes (anti-factor VIII-related antigen). (1) The blast cells of all the cases reacted with from at least two to at most eight different antibodies. Each antibody reacted with blast cells in a minimum of two (maximum 30) cases. (2) MT1, Ki-B3, anti-alpha 1-antichymotrypsin anti-neutrophil elastase, anti-S-100 protein, and MAC387 stained blast cells in more than 50% of the cases; MB1, L26, UCHL1, 4KB5, and DAKO-M1 in 20% to 50% of the cases; and anti-Leu-7 and anti-factor VIII-related antigen in less than 20% of the cases. (3) In the majority of cases many T lymphocytes, a small-to-moderate number of B lymphocytes, and a few Leu-7-positive lymphoid cells were intermingled with the blast cells. In some cases, especially where only a minor proportion of the blast cells was immunostained, it was nearly impossible to distinguish the lymphocytes of the tumor's stromal reaction from small blast cells. Thus, AML exhibits a heterogeneous immunophenotype in trephine biopsy specimens. Immunohistologic diagnosis of this disease in such specimens may be extremely difficult. Since staining of the blast cells with one or more of the antibodies generally used to define B cells, T cells, or their neoplastic derivatives is not uncommon, misinterpretation as non-Hodgkin's lymphoma of high-grade malignancy could easily occur. These findings also suggest that mixed-type (hybrid) acute leukemias with coexpression of myeloid and lymphoid cell markers could be more common than generally realized.

Multiple lineage reactivity in childhood leukemia

The leukemia cells from 63 children with acute leukemia were evaluated by flow cytometry with a panel of monoclonal antibodies that included lymphoid and myeloid lineage-specific antigens. Surface markers from patients with acute lyphocytic leukemia (ALL) did not correlate with their FAB classification except for L3 leukemia. Myeloid leukemias of FAB class M1-M4 were positive for CD13 and CD33, whereas CD14 and MY8 were only detected in FAB class M4 leukemia. Mixed leukemias were subclassified as intralineage (B+T+) or interlineage (B+ or T+/M+). Interlineage leukemias represented 5.6% of ALLs, and all patients are alive after treatment with ALL protocols. Interlineage mixed leukemias represent 7.9% of all leukemias occurring in 3.7% of ALLs and 33% of acute myeloid leukemias (AMLs). All children with mixed interlineage leukemias are alive after treatment with the protocol for the dominant leukemia; however, follow-up periods are too short to predict final outcome. The high proportion of mixed interlineage leukemias in AMLs supports Greaves' theory of lineage promiscuity, that is, there is a normal period of hematopoietic development when individual cells co-express multiple lineage antigens on the cell surface.