Hybrid acute leukaemia

Optimal therapeutic strategies for mixed phenotype acute leukemia

PURPOSE OF REVIEW

Mixed phenotype acute leukemia (MPAL) encompasses a rare group of clinically, immunophenotypically, and genetically diverse leukemias. Diagnosing and treating these patients remains challenging. In recent years, systematic efforts have been made to better define the genetic landscape of MPAL. These insights allow better understanding of the pathophysiology of MPAL, have the potential for a more biologically meaningful classification and may promote targeted, novel approaches to treat these leukemias.

RECENT FINDINGS

Recent studies suggest that MPALs originate in a multipotent primitive cell, demonstrate large genetic diversity and include subgroups that may benefit from targeted therapy. Recent data support the use of ALL-type induction followed by allogeneic stem cell transplantation in first remission for most adults. Novel targeted approaches hold promise for treatment of MPAL; however, some may unpredictably select for clonal expansion of cells from a different lineage than observed at presentation.

SUMMARY

A biologically and genetically driven classification of MPAL may yield more accurate prognosis and potentially direct therapy in patients with MPAL. Prospective efforts that incorporate targeted approaches based on genetics and immunophenotype are warranted.

Haematological profile of patients with mixed-phenotype acute leukaemia from a tertiary care centre of north India

Background & objectives:

Mixed-phenotype acute leukaemia (MPAL) is a rare neoplasm with no definite treatment protocols and a distinctly poor outcome. Advancement in polychromatic flow cytometry has made its identification easier. This prospective study was designed to identify cases of MPAL and study their clinical presentation and haematological profile in a tertiary care hospital in north India.

Methods:

Ethylenediaminetetraacetic acid (EDTA)-anticoagulated bone marrow aspirate samples of patients diagnosed as acute leukaemia (AL) on the basis of morphology were utilized for immunophenotyping. A comprehensive panel of fluorochrome-labelled monoclonal antibodies targeting myeloid, B-cell, T-cell and immaturity markers was utilized. The patients diagnosed to have MPAL, on the basis of the World Health Organization 2008 classification, were selected for further analyses.

Results:

There were 15 (2.99%) patients with MPAL of the total 501 cases of AL. Seven were children, all males and mean age of 5.08±3.88 yr. Eight were adults, male:female=6:2 and mean age of 21.43±5.74 yr. Eight were diagnosed as B/myeloid and seven were T/myeloid. No association was observed between age and immunophenotype of MPAL. On morphology, 11 were diagnosed as AML and four as ALL, and no specific morphology of blasts was predictive of a MPAL.

Interpretation & conclusions:

MPAL appeared to be a rare neoplasm (2.99% of AL cases). A comprehensive primary panel of monoclonal antibodies should be used to identify this neoplasm known to have a poor outcome.

Clinical and laboratory features of adult biphenotypic acute leukemia

AIM

To analyze the clinical and biological characteristics of adult BAL.

METHODS

We identified 22 cases (4.4%) of BAL from 496 newly diagnosed acute leukemia patients and compared them with patients with acute myloid leukemia (AML) and acute lymphoblastic leukemia (ALL).

RESULTS

CD34 positivity was higher in BAL (87%) than in ALL (60%, P = 0.04) and AML patients (63%, P = 0.05). The median age in the BAL group was greater than in ALL (43 vs 31 years, P = 0.04). Enlargement of liver, spleen and lymphonodes was more common in BAL (81.8%) than AML (46%, P = 0.003). Cytogenetic analysis revealed abnormal karyotypes in 56% of BAL patients. The overall completed remission rate in the BAL group (65%) was lower than in ALL (86%, P = 0.04).

CONCLUSION

BAL patients showed a much higher incidence of older age, CD34 antigen expression, presence of Philadelphia chromosome, liver, spleen and lymphonodes infiltration and resistance to therapy.

A unique cytogenetic abnormality, t(2;7)(p13.1;p21.3), in a Philadelphia-positive chronic myeloid leukemia

The Philadelphia (Ph) chromosome is present in more than 90% of patients suffering from chronic myeloid leukemia (CML). It is the product of a reciprocal translocation between the long arms of chromosomes 9 and 22, resulting in the transfer of the 3' portion of the proto-oncogene ABL from 9q34 to the 5' portion of the breakpoint cluster region (BCR) on 22q11. Currently, most CML cases are treated with Imatinib and variant rearrangements are thought to have no specific prognostic significance, although the events of therapy resistance have not yet been studied. In this study we report a novel case of CML exhibiting an uncommon t(2;7)(p13.1;p21.3) besides t(9;22)(q34;q11). This unusual translocation has been characterized by fluorescence in situ hybridization (FISH) and array-proven multicolor banding (aMCB), the latter being extremely significant in characterizing breakpoint regions in detail. The underlying mechanisms and prognostic implications of this cytogenetic abnormality are discussed in this study.

Clinical characteristics, biological profile, and outcome of biphenotypic acute leukemia: a case series

BACKGROUND

Biphenotypic acute leukemia (BAL) is a rare type of acute leukemia that presents with a high degree of heterogeneity and is not well defined.

METHODS

We identified 51 cases (3%) of BAL from 1,693 newly diagnosed acute leukemia patients according to the EGIL scoring system. The immunophenotyping, cytogenetics, treatment, and outcome of 39 BAL patients were retrospectively analyzed.

RESULTS

There were 23 (59%) cases of the myeloid and B-lymphoid phenotype, 14 (36%) cases of the myeloid and T-lymphoid phenotype, and 1 case (3%) of the trilineage phenotype or B/T phenotype. Abnormal karyotypes were detected in 76% of the 37 validated patients and displayed a high degree of heterogeneity. Combined regimens for both acute myeloid leukemia (AML) and acute lymphoid leukemia (ALL), as well as ALL type regimens, appeared to achieve a better complete remission rate than AML type regimens (71 and 64 vs. 33%, respectively). BAL patients with complex karyotypes or a rearrangement of chromosome 11 had a significantly reduced survival rate in comparison to patients with normal, t(8; 21), or t(9; 22) karyotypes. The probability of overall survival and disease-free survival at 2 years was 26 and 18%, respectively.

CONCLUSIONS

Our findings indicate that BAL shows a high incidence of abnormal karyotypes and a poor prognosis. Combined-type regimens or ALL-based protocols are effective for the treatment of BAL.

Lineage switch from precursor B cell acute lymphoblastic leukemia to acute monocytic leukemia at relapse

A lineage switch in leukemia, in which the leukemic cell lineage at onset converts to another lineage at a later time, is an uncommon type of hybrid (mixed) leukemia regarded as a variation of bilineage leukemia. We present a case of a 60-year-old female diagnosed with precursor B cell acute lymphoblastic leukemia (ALL), whose markers in flow cytometry shifted from their original status of CD19+, 22+, 79a+, 13+, HLA-DR+, and TdT+. Although her bone marrow achieved remission after induction therapy, there was a small residual population of leukemic cells in the liver. Residual disease was proved by biopsy and pathologically shown to have an immature phenotype of CD5+, CD10-, CD20-, CD79a- and myeloperoxidase negativity. Two weeks after liver biopsy, blast cells progressively appeared in the peripheral blood; these cells had a monocytoid morphology and phenotype (CD13, 14) but were accompanied by myeloid (CD33) and lymphoid (CD2, 4, 20) cells. Markers CD7, 10 and 19 were negative by flow cytometry. This phenotypical conversion from B-ALL to hybrid leukemia featuring monocytoid characteristics is known as a lineage switch. This case suggests that leukemic subclones tend to carry out dedifferentiation, occasionally in extramedullary sites, which serve as a hotbed for the selection of resistant clones.

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.

Molecular and phenotypic analysis of Philadelphia chromosome-positive bilineage leukemia: possibility of a lineage switch from T-lymphoid leukemic progenitor to myeloid cells

The occurrence of acute bilineage leukemia is thought to be the malignant transformation of a myeloid or lymphoid leukemic progenitor with the potential to differentiate into the other lineages; however, the mechanisms of this lineage switch are not well understood. Here, we report on the extremely rare case of adult Philadelphia chromosome-positive acute bilineage leukemia, which is characterized by T-cell acute lymphoblastic leukemia and acute myelomonocytic leukemia. Chromosome analysis showed 46,XY,del(7)(p11.2),t(9;22)(q34;q11.2) in all metaphases and a minor BCR/ABL chimeric gene was detected in these leukemic cells by PT-PCR. When the CD5+ and CD5- cells were sorted, a fusion gene of BCR/ABL and the same clonally rearranged band of a T-cell receptor (TCR) gene were detected in both populations. Nucleotide sequencing of the TCR-gamma gene revealed the clonal rearrangement of the V8-JGT2 complex in both populations. Overexpression of PU.1, which plays a fundamental role in myelomonocyte development, was found in the sorted CD34+CD7+ and CD5-, but not CD5+ cells. These results suggest that leukemic progenitor cells in the T-lineage with the del(7) and t(9;22) have the potential to differentiate into myeloid lineage, and that enforced PU.1 expression may contribute in part of this phenomenon.

Trisomy 4 as the sole karyotypic abnormality in a case of acute biphenotypic leukemia with T-lineage markers in minimally differentiated acute myelocytic leukemia

We report an unusual case of acute biphenotypic leukemia with trisomy 4. A 22-year-old woman presented with acute leukemia characterized by the presence of two cell populations (prothymocytic and myeloblastic). The leukemic cells were resistant to standard induction chemotherapy and were cleared from the bone marrow only after a salvage chemotherapy regimen. To our knowledge, this is the fourth reported case of acute biphenotypic leukemia with trisomy 4 and perhaps the first case with T-lineage markers and acute myelocytic leukemia.

Fetal liver myelopoiesis occurs through distinct, prospectively isolatable progenitor subsets

Hematopoietic fate maps in the developing mouse embryo remain imprecise. Definitive, adult-type hematopoiesis first appears in the fetal liver, then progresses to the spleen and bone marrow. Clonogenic common lymphoid progenitors and clonogenic common myeloid progenitors (CMPs) in adult mouse bone marrow that give rise to all lymphoid and myeloid lineages, respectively, have recently been identified. Here it is shown that myelopoiesis in the fetal liver similarly proceeds through a CMP equivalent. Fetal liver CMPs give rise to megakaryocyte-erythrocyte-restricted progenitors (MEPs) and granulocyte-monocyte-restricted progenitors (GMPs) that can also be prospectively isolated by cell surface phenotype. MEPs and GMPs generate mutually exclusive cell types in clonogenic colony assays and in transplantation experiments, suggesting that the lineage restriction observed within each progenitor subset is absolute under normal conditions. Purified progenitor populations were used to analyze expression profiles of various hematopoiesis-related genes. Expression patterns closely matched those of the adult counterpart populations. These results suggest that adult hematopoietic hierarchies are determined early in the development of the definitive immune system and suggest that the molecular mechanisms underlying cell fate decisions within the myeloerythroid lineages are conserved from embryo to adult. (Blood. 2001;98:627-635)

The c-kit receptor and its ligand stem cell factor in childhood malignant lymphoid precursors

The c-kit receptor (CD117) and its ligand stem cell factor (SCF) play an important role in the development, differentiation, and survival of normal and malignant hematopoietic cells. The aim of this work is to review the cellular distribution of this receptor and the effect of SCF on the hematopoietic system, particularly among lymphoid lineage, either in normal or malignant cell progenitors. We examined reports and results in the field and articles or abstracts published in journals covered by MEDLINE. Additionally, we evaluated CD117 expression on fresh blast cells of 376 newly diagnosed cases of childhood acute lymphoblastic leukemia (ALL) that were referred to centers affiliated with the Italian Association for Pediatric Hematology and Oncology (AIEOP). In view of our data, approximately 11% of ALL are CD117 positive. In particular, this receptor can be expressed in 10% and 11.5% of T-lineage and B-lineage ALL, respectively. Its expression is associated with an intermediate/mature phenotype in T-lineage ALL, whereas in B-lineage ALL, the majority of the positive cases are classified as early B ALL. The effect of SCF on malignant hematopoiesis and its potential clinical uses are reviewed.

Double G0/G1 peak in the DNA histogram of aberrant marker positive acute leukemia patients is associated with a poor clinical outcome

In order to investigate the relationship between aberrant marker expression and DNA ploidy, 61 adult patients with acute leukemia (39 AML and 22 ALL) were studied. Aberrant marker expression was observed in 20 patients (16/39 of AML and 4/22 of ALL patients). In flow cytometric DNA analysis aneuploidy was observed in 18 patients (9/39 of AML and 9/22 of ALL patients). The incidence of aneuploidy in patients with aberrant marker expression was 35% whereas this was 26.8% in patients without aberrant marker expression. Furthermore, 7 patients with aberrant marker expression showed an aneuploid, double G0/G1 peaks appearance whereas the remaining 11 patients with aberrant marker expression had euploid DNA content. Double G0/G1 appearance was not observed in patients without aberrant marker expression. Further analyses revealed that this did not correlate with apoptosis. All 7 patients, who had both aberrant marker expression and double G0/G1 peak had a poor clinical outcome with a short survival and all died within three months whereas three-months survival was 67% for AML, 69% for ALL patients and 81% for patients with aberrant marker expression respectively (p<0.01). Our data indicate that the evaluation of the DNA ploidy in patients with aberrant marker expression may be of prognostic importance.

Expression of Myeloid Markers Lacks Prognostic Impact in Children Treated for Acute Lymphoblastic Leukemia: Italian Experience in AIEOP-ALL 88-91 Studies

The importance of coexpression of myeloid antigens in childhood acute lymphoblastic leukemia (ALL) has long been debated; results are conflicting. We studied children with ALL treated at Italian Association for Pediatric Hematology-Oncology (AIEOP) institutions over 6 years with Berlin-Frankfurt-Muenster (BFM)-based protocols and have analyzed the incidence of coexpression of six MyAg (CD11b, CD13, CD14, CD15, CD33, CD65w) to determine its prognostic impact. Criteria for MyAg coexpression (MyAg+ALL) included positivity to one or more MyAg on at least 20% of blasts and confirmation of coexpression at double-fluorescence analysis. A total of 291 of 908 cases were MyAg+ALL (32%). Incidence was similar in B-ALL and T-ALL; among common, pre-B, and pre-pre–B-ALL. CD13 and CD33 were most common. Patients with MyAg+ALL had presenting features similar to MyAg−ALL. They entered standard or intermediate risk protocols more frequently and had better prednisone response, but similar complete remission rates. Six-year event-free survival (EFS) was 69.0% in 291 MyAg+ALL cases and 65.3% in 617 MyAg−ALL cases, without significant difference. Cases expressing two or more MyAg presented similar clinical features and treatment response. MyAg+ALL had worse EFS only in infants (0% v47%) (P = .01). Therefore, in this series of homogeneously diagnosed and treated ALL, coexpression of MyAg was not associated with prognostic significance, without relevance for clinical purposes or for patient stratification, except for infants.

© 1998 by The American Society of Hematology.

Expression of Myeloid Markers Lacks Prognostic Impact in Children Treated for Acute Lymphoblastic Leukemia: Italian Experience in AIEOP-ALL 88-91 Studies

The importance of coexpression of myeloid antigens in childhood acute lymphoblastic leukemia (ALL) has long been debated; results are conflicting. We studied children with ALL treated at Italian Association for Pediatric Hematology-Oncology (AIEOP) institutions over 6 years with Berlin-Frankfurt-Muenster (BFM)-based protocols and have analyzed the incidence of coexpression of six MyAg (CD11b, CD13, CD14, CD15, CD33, CD65w) to determine its prognostic impact. Criteria for MyAg coexpression (MyAg+ALL) included positivity to one or more MyAg on at least 20% of blasts and confirmation of coexpression at double-fluorescence analysis. A total of 291 of 908 cases were MyAg+ALL (32%). Incidence was similar in B-ALL and T-ALL; among common, pre-B, and pre-pre–B-ALL. CD13 and CD33 were most common. Patients with MyAg+ALL had presenting features similar to MyAg−ALL. They entered standard or intermediate risk protocols more frequently and had better prednisone response, but similar complete remission rates. Six-year event-free survival (EFS) was 69.0% in 291 MyAg+ALL cases and 65.3% in 617 MyAg−ALL cases, without significant difference. Cases expressing two or more MyAg presented similar clinical features and treatment response. MyAg+ALL had worse EFS only in infants (0% v47%) (P = .01). Therefore, in this series of homogeneously diagnosed and treated ALL, coexpression of MyAg was not associated with prognostic significance, without relevance for clinical purposes or for patient stratification, except for infants.

© 1998 by The American Society of Hematology.

Large granular lymphocytic leukaemia with a mixed T-cell/B-cell phenotype

We report a case of large granular lymphocytic leukaemia (LGLL) with mixed T-cell/B-cell phenotypes. The LGLL cells expressed T-cell markers such as CD1, CD2, CD3, CD5, CD7, CD8 and CD57. The CD8+ LGLL cells coexpressed B-cell markers including CD20 and PCA-1, and a fraction of purified CD8+ LGLL cells secreted double isotypes of immunoglobulins (IgG-kappa and IgA-kappa). Both TCRB and IGH genes were clonally rearranged. The LGLL cells could be divided into at least three subpopulations that were cytogenetically distinct, and all subpopulations involved the 11q23. The expression of both T- and B-cell markers on the LGLL cells suggests the involvement of a putative common lymphoid progenitor in leukaemic transformation.

Adult biphenotypic acute leukaemia: an entity with poor prognosis which is related to unfavourable cytogenetics and P-glycoprotein over-expression

Biphenotypic acute leukaemia (BAL) patients represented 8% of the 287 de novo consecutive adult acute leukaemias (23 BAL, 230 acute myeloid leukaemia (AML) and 34 acute lymphoblastic leukaemia (ALL)) referred to our department during the last 4-year period. Of these 23 BAL patients, 14 patients showed myeloid morphology and nine cases lymphoid morphology according to FAB criteria. There were no differences between lymphoid and myeloid BAL according to clinical and biological presentation and treatment outcome. We confirm the poor prognosis of BAL when compared to AML or ALL seen during the same period of time, in terms of complete remission (47%, 62% and 82% respectively, BAL v AML, NS and BAL v ALL, P = 0.006) and 4-year overall survival (8.1%, 25.8% and 23.8% respectively, BAL v AML, P = 0.05 and BAL v ALL, P = 0.003). Comparing adult BAL patients with AML patients, we found an increase in poor prognostic factors: CD34+ phenotype (82% v 60% respectively, P = 0.03), unfavourable karyotype (60% v 20%, P < 0.0001) and Pgp over-expression by RT-PCR (0.705 v 0.107, P < 0.0001) and flow cytometry (0.824 v 0.391, P = 0.0001). MRP and LRP were not found to be poor prognostic factors. Comparing BAL patients with ALL patients, we found also an increase in poor prognostic factors: age (51 v 39, P = 0.003) and CD34+ phenotype (82% v 50%, P = 0.02). We conclude that BAL patients need a more aggressive treatment procedure, including high-dose AraC or the use of Pgp modulators for first-line therapy.

Coexpression of lymphoid and myeloid markers on cell surfaces

Cells coexpressing lymphoid and myeloid cell surface markers have been described for various leukemias and non-Hodgkin's lymphomas. It is unclear whether these mixed lineage characteristics are due to malignancies of early progenitor cells or alternatively to malignant cells with lineage infidelity. Recently, it has been shown that cells coexpressing lymphoid and myeloid markers can be generated from peripheral blood lymphocytes from normal individuals as well. In this review, consequences of this surprising fact are discussed.

Biphenotypic blast crisis of chronic myelogenous leukemia: abnormalities of p53 and retinoblastoma genes

The molecular mechanisms responsible for progression of chronic myelogenous leukemia (CML) to blast crisis have not been well defined. Blast crisis may be partially related to inactivation of tumor suppressor genes/such as p53 or retinoblastoma (Rb) gene. There is evidence for an association of blast cell phenotypes in CML with alterations of these genes: a strong association of myeloid phenotypes with abnormalities of the p53 gene and a weaker association of lymphoid phenotypes with abnormalities of the Rb system. We found a marked decrease in Rb gene product and rearrangements of the p53 gene simultaneously in two cases of biphenotypic blast crisis of CML (myeloid and B-lymphoid). These results support the association of blast cell phenotypes with alterations in tumor suppressor genes in CML blast crisis.

Bilineal acute leukemia of B and T lineage with a novel translocation t(9;17)(p11;q11)

We describe a case of bilineal leukemia in a 5-year old boy with a rare immunophenotype and the novel translocation t(9;17)(p11;q11) as the sole chromosomal abnormality. Two immunologically distinct blast cell subsets expressed T-markers (CD2, CD5, CD7) and common ALL markers (TdT, CD19, CD22, CD10), respectively. Both cell populations were CD34 negative. The patient, who presented with CNS leukemia, responded promptly to standard chemotherapy for lymphoblastic leukemia and remains in complete remission 20 months from diagnosis. Other translocations between chromosomes 9 and 17 have been infrequently reported in a variety of leukemias but as yet their biologic significance is unknown. The clinical course of this case suggests that t(9;17)(p11;q11) may not have an adverse influence on the disease outcome. However, the role of t(9;17) in the pathogenesis of this unusual lymphoid phenotype remains unresolved.

Biphenotypic leukemia with a new translocation, t(2;6)(q31;q23)

A t(2;6)(q31;q23) was found in a patient with acute biphenotypic leukemia. This cytogenetic change has not been reported previously in acute lymphocytic leukemia (ALL) or biphenotypic leukemia, although deletion of 6q has been frequently found in ALL.

Immunophenotyping of AML and MDS and detection of residual disease

Immunophenotyping improves both accuracy and reproducibility of the FAB classification and is considered particularly useful for identifying poorly differentiated FAB subtypes of AML, such as AML with minimal differentiation (M0), microgranular promyelocytic leukaemia (M3V), and megakaryoblastic leukaemia (M7). Immunological studies of myeloid leukaemic blasts has become critical also in identifying biphenotypic leukaemias and AML expressing lymphoid-associated markers (Ly+ AML). At present, while the prognostic value of individual antigen expressions is still controversial, due to technical questions, the immunological detection of MRD seems to be important in monitoring AML patients in remission and, perhaps, in detecting leukaemic cell contamination into bone marrow or peripheral blood progenitor cells collected for autologous transplantation. In addition, the relationship established between genetic abnormalities and certain phenotypes within different FAB subtypes suggests that, in the future, immunophenotypical studies could be used for the screening of AML cases carrying specific genetic aberrations. Compared to acute leukaemias, little information is available concerning immunological patterns in MDS, and the role of the immunophenotype in diagnosis, subclassification, and prognosis of MDS is currently not well established.

Acute leukemic transformation of myelodysplastic syndrome--immunophenotypic, genotypic, and cytogenetic studies

The clinical and biological characteristics of myelodysplastic syndrome (MDS) in acute leukemic transformation were studied in 23 patients. All had myeloid transformation according to FAB criteria, but coexpression of lymphoid-associated antigens was detected in five of the 20 patients who underwent an immunophenotypic study. Rearrangement of the immunoglobulin heavy chain gene was also observed in one of the five patients who coexpressed lymphoid markers and that of the T-cell receptor beta chain gene in another one. None had pure lymphoid transformation. Clonal chromosomal abnormalities were noted in 12 (63%) of the 19 patients who underwent cytogenetic study, most commonly - 7 (six patients or 32%). In the 18 patients who underwent serial analyses both at MDS diagnosis and at acute transformation, seven (39%) underwent karyotypic evolution. The most common new or additional aberrations were +8 and +21. N-ras gene mutation was detected in two of the nine patients at acute leukemic transformation. The median interval from diagnosis of MDS to onset of acute transformation was 10 months (1-36 months). Patients with a normal karyotype at diagnosis had a significantly longer chronic phase duration than those with chromosomal abnormalities (median of 20 months vs. 5 months). However, all had a short survival time after diagnosis of acute leukemia, whether chromosomal anomalies were present or not.

Exogenous expression of human granulocyte colony-stimulating factor receptor in a B-lineage acute lymphoblastic leukemia cell line: a possible model for mixed lineage leukemia

We report evidence that the granulocyte colony-stimulating factor (G-CSF) receptor is present and may be functioning on blast cells from some patients with myeloid surface antigen positive (My+) acute lymphoblastic leukemia (ALL). In the present study, a human G-CSF receptor expression plasmid was transfected into a newly established B-lineage ALL cell line 'Tanoue' and its subclone 'ST' by lipofection to investigate whether expression of the G-CSF receptor and G-CSF stimulation would induce myeloid characteristics on myeloid surface antigen negative (My-) ALL cells. The G-CSF receptor became detectable on the transfected cells (GR-Tanoue and GR-ST), with dissociation constant values of 50-130 pmol/l, and maximal binding sites (Bmax of 77-6100 sites/cell on receptor binding assays. Short term culture with recombinant human G-CSF induced myeloid differentiation (a two to three-fold increase in CD33 and CD15 expression), and a moderate 3H-thymidine uptake (stimulation index, 1.75) only in the GR-ST clone no. 15 which expressed a high number of G-CSF receptors (Bmax, 6100 sites/cell). Our data show that (a) exogenous expression of the G-CSF receptor and G-CSF stimulation can induce myeloid characteristics on ALL cells; and (b) in the G-CSF receptor-expressing cells, there is a correlation between the number of G-CSF receptors and cell responsiveness to G-CSF in either proliferation or differentiation.

CD7 expression in acute myeloid leukemia

The clinical significance of the expression of CD7 antigen on the blasts of 207 consecutive patients with de novo acute myeloid leukemia (AML) was evaluated. For this purpose, fifty-three CD7+ patients (23 females and 30 males; mean age 52 years) were analyzed and classified into the following subtypes according to French-American-British (FAB) classification: 7 M0, 13 M1, 9 M2, 1 M3, 9 M4, 14 M5. Immunophenotypic studies were carried out by flow cytometry and blast cells were selected on the basis of forward light scatter gating and pan-myeloid marker, either CD13 or CD33. All the CD7+ patients were negative for surface CD3 and T-cell-receptor (TCR) molecules. We found no correlation between CD7 expression and sex, age, hepatosplenomegaly and/or central nervous system involvement. The immaturity of CD7+ leukemic cells was supported by the high expression of CD34 (P = 0.001). CD7 positivity was significantly associated with a white blood cell count (WBC) greater than 100 x 10(9)/L (P = 0.003). P-Glycoprotein (P-170) expression was also evaluated in 135 patients by a flow-cytometric assay: there was a close relationship between CD7 and P-170 positivity (P < 0.001). For remission induction, all patients received therapeutic regimens routinely used for AML. The complete remission (CR) rate was significantly lower in CD7+ cases (32% vs 74%, P = 0.001). The overall survival and disease free survival rate of CD7+ AML was lower than those of CD7- patients (P < 0.001 and = 0.002, respectively). CD7+ AML with coexpression of CD14 had a particularly unfavourable response and prognosis in comparison with CD7+ patients without CD14.(ABSTRACT TRUNCATED AT 250 WORDS)

Heavy-chain immunoglobulin gene rearrangement and cytoplasmic immunoglobulin expression in acute monocytic leukemia following primary germ cell tumor

A case of acute monocytic leukemia with rearrangement of the immunoglobulin heavy-chain gene and strong cytoplasmic immunoglobulin expression in a young patient treated with multi-drug chemotherapy for primary seminomatous germ cell tumor 13 months earlier is reported. The short latency period from the beginning of therapy for primary germ cell tumor and the abrupt onset of leukemia with no identifiable prodrome bear similarities to podophyllotoxin-related leukemias.

Usefulness of immunocytochemistry for phenotypical analysis of acute leukemia; improved fixation procedure and comparative study with flow cytometry

We investigated the phenotypes of blast cells of 53 patients with acute leukemia by a modified streptavidin-biotin alkaline phosphatase (SAB-AP) labeling technique, using a panel of monoclonal antibodies [MoAb; anti-CD11b, CD13, CD14, CD33, CD34, CD41, CD3, CD7, CD10, CD19, anti-HLA-DR, and anti-myeloperoxidase (MPO)]. The selection of an optimal fixative solution for each antigen from five options of various combinations of formalin, acetone, methanol, and/or ethanol, successfully conserved cell morphology and improved specific reaction compared with the conventional methods which used a single fixative for multiple antigens. We compared the SAB-AP results with those obtained by flow cytometry (FCM) for surface markers in each case. High concordance rates for both positive and negative results were observed for each marker. However, positive reaction for some markers (anti-CD13, CD14, CD33, and CD34) were often noted only in the cytoplasm by the SAB-AP method, indicating that combination of these two methods is essential for the precise immunophenotyping of poorly differentiated leukemia cells.

Molecular analysis of CD2 gene expression in acute myeloblastic leukemia expressing T-lineage associated surface antigens

CD2 is a surface marker of T cells and NK cells, and is not normally expressed on human myeloid cells, but is found on a significant minority of cases of acute myeloid leukemia (AML). Molecular studies were performed on bone marrow myeloblasts from two patients with CD2 surface positive AML. No abnormality of the CD2 gene was detected on Southern blot analysis. On Northern blots, CD2 mRNA of normal size was present. The CD2 gene contained a site which was unmethylated, consistent with active transcription, in a CD2 positive AML case, and in a CD2 positive T cell line, but methylated in CD2 negative AML cells. The evidence does not support the hypothesis that inappropriate surface expression of lineage markers is due to leukemia-related genetic changes, such as amplification or rearrangement, of the CD2 gene itself. Rather, the results are consistent with the hypothesis that mixed lineage leukaemia arises from rare normal bone marrow progenitors with multilineage phenotypes.

Recommended procedures for the classification of acute leukaemias

The classification of acute leukaemias is now widely based on a combined morphological, cytochemical and immunophenotyping approach. Difficulties are frequently encountered however in reaching an acceptable degree of diagnostic concordance between different laboratories because of variations in the techniques used (in terms of methodologies, reagents and equipment) and diagnostic interpretation. The International Council for Standardization in Haematology (ICSH) convened an expert panel to consider currently available diagnostic techniques with the aim of defining a minimum cytochemical and immunological diagnostic panel that could be used as core components for the classification of acute leukaemia. The proposed ICSH scheme, which attempts to balance the basic requirement for providing precise and informative diagnostic information without limiting its use to only those laboratories with sophisticated facilities, is based on three sequential levels of investigation; primary cytochemistry, intracellular phenotyping and membrane immunophenotyping. The minimum ICSH recommended cytochemistries comprise myeloperoxidase (MPO), chloroacetate esterase (ChlorE) and alpha-naphthyl acetate esterase (ANAE), and standardised methods for these cytochemistries are detailed in this communication. For cases of acute leukaemia that remain unclassified by primary cytochemistry, subsequent immunological analyses for cytoplasmic CD3, CD22, MPO and nuclear TdT are recommended. The ICSH panel considers that the use of these minimum primary cytochemical and intracellular phenotyping procedures will lead to the consistent classification of most acute leukaemias, and that the third level of investigation (membrane immunophenotyping) should be used for the purposes of confirmation, diagnostic clarification of atypical leukaemias, and the subtyping of acute lymphoblastic leukaemias (ALL). The ICSH panel also recognised that there are a number of additional technologies which can provide definitive diagnostic information, such as cytogenetics and DNA genotyping, but these were excluded from the minimum panel because of their restricted availability. While many specialised laboratories, particularly in the areas of diagnostic research, will continue to use individual investigatory protocols, it is considered that the inclusion of the ICSH scheme as core components would lead to greater consistency when comparing independent studies of acute leukaemia.

Cytogenetics of hybrid acute leukemias

Although the recognition of hybrid acute leukemia (HAL) is still controversial, several reports have described cytogenetic findings in these leukemias over the last 3 years. A distinct chromosomal profile appears to be associated with different immunologic subsets of HAL. The classical t(15;17), and inv(16) as well as abnormalities of the long arm of chromosome 5 and/or 7 are preferentially associated with acute myeloid leukemia (AML) with T-cell features; the t(8;21)(q22;q22), the Ph chromosome, and 11q23 rearrangements are more frequently found in AML with B-cell features; the Ph chromosome, t11q23 and 14q32 breaks without rearrangements of the immunoglobulin heavy chain gene may be associated with acute lymphoblastic leukemia (ALL) with myeloid markers. In addition, some chromosome aberrations may be encountered more frequently in acute leukemia with major phenotype deviations than in unselected cases of acute leukemia: namely the Ph chromosome, 11q23 rearrangements, and +13. These chromosome changes appear to be associated with a low complete remission (CR) rate. An association has been documented in some patients with ALL between the presence of the t(9;22) and a minor myeloid component consisting of 5-15% blast cells with myelomonocytic features, raising the possibility that a diagnosis of bilineal acute leukemia would be more appropriate in such cases. These patients appear to have a severe outcome with significantly lower CR rate than similar cases of Ph-positive ALL without a minor myeloid component.(ABSTRACT TRUNCATED AT 250 WORDS)

Cytokines and cytokine receptors in acute lymphoblastic leukemia expressing myeloid markers--role in growth regulation

There is no evidence that cancer cells including leukemic cells are immortal. It has been clearly indicated that certain cytokines can significantly stimulate leukemic cell proliferation in vitro, and sustain the circuit of autocrine or paracrine stimulation. The biological roles of cytokines and cytokine receptors have been intensively investigated in acute leukemia. Recently coexpression of both lymphoid and myeloid features on a single leukemic cell has been well recognized using a flowcytometric technique. Studies of ALL cells expressing myeloid markers (My+ ALL) have indicated that the profiles of cytokines and cytokine receptors expressed by My+ ALL show both similarities and differences to those in My- ALL or acute myelogenous leukemia (AML), suggesting that My+ ALL cells may originate from uncommitted hematopoietic precursor cells coexpressing features of both lymphoid and myeloid lineages. The exact assessment of cytokine response of leukemic cells would provide an important tool for phenotyping acute leukemia based on the growth properties of the cells (cytokine phenotyping), in addition to the morphologic classification and immunological surface phenotyping. Additionally alteration of sensitivity to cytotoxic anticancer drugs by cytokine stimulation may be the new strategy for biologic therapy of acute leukemia.

The c-kit molecule and the surface immunophenotype of human acute leukemia

The proto-oncogene c-kit encodes the receptor for a stem cell factor (c-kit molecule). Expression of the c-kit molecule on the gated leukemic blast cells from newly diagnosed patients with leukemia was analysed by flow cytometry using the monoclonal antibody (17F11). Among 35 myeloid leukemia cases examined, significant c-kit-positive blast cells were detected in 24 cases (69%), even though the percentage of positive cells was widely variable. The correlation between the percentage of cells positive for the c-kit molecule and the percentage of cells positive for CD34 was found to be statistically significant (rs = 0.36, p < 0.05). Fifteen cases of myeloid leukemia were positive for lymphoid markers. The mean percentage of the cells expressing c-kit molecule among the lymphoid marker-positive cases was significantly larger than that among the lymphoid marker-negative cases (p < 0.05). All 19 lymphoid leukemia cases were c-kit-negative, including 8 cases which were positive for some myeloid markers. Stem cell factor enhanced the colony growth in five out of six acute myeloblastic leukemia cases expressing the c-kit molecule. On the other hand, SCF did not stimulate colony growth in any of the four cases which were not positive for the c-kit molecule. These findings indicated that the distribution of flow cytometrically detectable c-kit molecules on leukemic cells is related to the morphologic and immunologic classification of these leukemic cells and to the expression of the CD34 cell surface molecule on some myeloid leukemic cells. On such cells, expression of the c-kit molecule may have a functional role and be related to the maturation process.

Minor myeloid component in Ph chromosome-positive acute lymphoblastic leukaemia: correlation with cytogenetic pattern and implication for poor response to therapy

Morphological, immunological and cytogenetic features were studied in 27 adults presenting with Ph chromosome-positive acute lymphoblastic leukaemia (ALL), in correlation with clinical outcome. Twenty patients (group 1) were diagnosed as having typical ALL according to the FAB criteria supported by immunological findings. Less than 1% blast cells with azurophilic granules were detected in all cases. Myeloid cytochemistry, i.e. peroxidase and Sudan black-B stain, was negative in all cases. A minor phenotype deviation consisting of the expression of the CD13 myeloid-associated marker was detected in two patients. In seven patients (group 2) a diagnosis of ALL with a minor myeloid component was made because of the presence of a majority of lymphoid blasts and of 5-15% blast cells with morphological cytochemical and immunological features of the myeloid lineage. Abnormal metaphases were found in 6/20 (30%) patients in group 1, compared with 7/7 (100%) patients in group 2. All patients were treated by antilymphoid regimens; however, complete remission was achieved in 17/20 (85%) patients in group 1 versus 1/7 (14.3%) patients in group 2. Median survival was 16 months, range < 1-120+ in group 1 and 9 months, range < 1-15 in group 2. It is concluded that morphological, immunological and cytogenetic studies allow for the recognition of two cytological subsets of Ph+ ALL. The presence of a minor myeloid component in otherwise typical Ph chromosome-positive ALL may be associated with a distinct cytogenetic pattern and poor responses to antilymphoid therapy.

Peroxidase expression in acute unclassified leukemias: ultrastructural studies in combination with immunophenotyping

The lineage affinity of 61 cases of acute unclassified leukemias (AUL) was reevaluated by ultrastructural analysis of peroxidase expression (POEM) in combination with immunophenotyping. In 24 cases a significant proportion of the blasts displayed ultrastructural myeloperoxidase (UMPO) and in another 3 cases platelet peroxidase (UPPO) suggesting the allocation of these leukemias to the myeloid or megakaryoblastic lineage. No significant correlation between myeloid surface marker expression and POEM positivity could be detected, while the presence of the CD 19 or CD 24 antigen significantly correlated with POEM negativity. The detection of lymphoid markers on POEM+ blasts indicates, that these leukemias might be derived from bipotential progenitors, which have retained their lymphoid antigens during myeloid differentiation. In one case a bilineage leukemia with a POEM+/CD 19- and a POEM-/CD 19+ population could be identified by immunoelectron microscopical studies (IEM). The remaining 34 AUL cases were POEM negative. Combined data suggest that these cases probably derive from early lymphoid progenitors. Taken together, AUL are heterogenous in presentation and in their cellular origin including a major portion of cases with an unequivocal myeloid differentiation detectable by ultrastructural analysis of myeloperoxidase expression.

Phenotypic characteristics of acute megakaryocytic leukemia and transient abnormal myelopoiesis

By immunophenotyping and ultrastructural cytochemistry, the disorders involving megakaryocytic lineage cells have been clarified. These disorders are termed acute megakaryocytic leukemia (AMKL) and transient abnormal myelopoiesis (TAM). The characteristics of blasts in these disorders have been extensively investigated from various standpoints including cytochemistry, cytogenetics, ultrastructure and in vitro-colony differentiation. The target cells of AMKL and TAM are immature cells close to stem cells which are capable of differentiating into lineage cells such as megakaryocytes, erythrocytes and myeloid cells. Phenotypically, these blasts frequently express antigens appearing at an early stage in the hematopoietic differentiation pathway. They thus often emerge as mixed phenotypes as seen in mixed lineage leukemia of immature cell origin.

Clinical relevance of acute mixed-lineage leukemias

Conflicting results have been reported in recent years concerning the incidence and prognostic relevance of acute mixed-lineage leukemias (AMLL). Among the high number of possible hybrid antigen combinations, it is important to discriminate those occurring with sufficient frequency to be of general clinical significance. In this review an approach to a classification based upon the hierarchical import of developmental antigens seen during hemopoietic differentiation is suggested. As far as the clinical relevance of AMLL is concerned, some hybrid patterns have been found to be associated with distinct characteristics in terms of clinical features at the time of presentation and poor response to treatment. For these particular types of leukemia, the time has probably arrived to design more specific therapeutic regimens.

The diagnostic and prognostic value of immunophenotyping in acute leukemia

Immunophenotyping with monoclonal antibodies to leucocyte differentiation antigens has an established diagnostic role in the laboratory investigation of acute leukemia. In the vast majority of cases, a hemopoietic lineage can be confidently assigned; namely, acute myeloid leukemia (AML), or the precursor-B and precursor-T variants of acute lymphoblastic leukemia (ALL). The areas of greatest practical importance are in morphologically difficult or undifferentiated cases, and in distinguishing between the major variants of precursor-B and T-ALL. Cases with aberrant patterns of marker expression (acute mixed lineage leukemia, lineage infidelity) are frequently encountered in both ALL and AML, and can lead to diagnostic confusion. However, correlation with morphology and other clinicopathologic features, and careful consideration of the weight of phenotyping evidence almost always allows the correct lineage to be identified. The prognostic value of phenotypic information in acute leukemia is generally limited. Recognition of the major variants of ALL is still of clinical importance, but the significance of myeloid antigen positivity in ALL is controversial, and may not have prognostic value. Patterns of myeloid antigen expression in AML have limited prognostic significance, while the relationship between lymphoid antigen expression and treatment response in AML remains highly controversial. Careful evaluation of the predictive power of immunophenotype in large controlled clinical trials in acute leukemia is still required.

Recommended procedures for the classification of acute leukaemias. International Council for Standardization in Haematology (ICSH)

The classification of acute leukaemias is now widely based on a combined morphological, cytochemical and immunophenotyping approach. Difficulties are frequently encountered however in reaching an acceptable degree of diagnostic concordance between different laboratories because of variations in the techniques used (in terms of methodologies, reagents and equipment) and diagnostic interpretation. The International Council for Standardization in Haematology (ICSH) convened an expert panel to consider currently available diagnostic techniques with the aim of defining a minimum cytochemical and immunological diagnostic panel that could be used as core components for the classification of acute leukemia. The proposed ICSH scheme, which attempts to balance the basic requirement for providing precise and informative diagnostic information without limiting its use to only those laboratories with sophisticated facilities, is based on three sequential levels of investigation; primary cytochemistry, intracellular phenotyping and membrane immunophenotyping. The minimum ICSH recommended cytochemistries comprise myeloperoxidase (MPO), chloroacetate esterase (ChlorE) and alpha-naphthyl acetate esterase (ANAE), and standardised methods for these cytochemistries are detailed in this communication. For cases of acute leukaemia that remain unclassified by primary cytochemistry, subsequent immunological analyses for cytoplasmic CD3, CD22, MPO and nuclear TdT are recommended. The ICSH panel considers that the use of these minimum primary cytochemical and intracellular phenotyping procedures will lead to the consistent classification of most acute leukaemias, and that the third level of investigation (membrane immunophenotyping) should be used for the purposes of confirmation, diagnostic clarification of atypical leukaemias, and the subtyping of acute lymphoblastic leukaemias (ALL). The ICSH panel also recognised that there are a number of additional technologies which can provide definitive diagnostic information, such as cytogenetics and DNA genotyping, but these were excluded from the minimum panel because of their restricted availability. While many specialised laboratories, particularly in the areas of diagnostic research, will continue to use individual investigatory protocols, it is considered that the inclusion of the ICSH scheme as core components would lead to greater consistency when comparing independent studies of acute leukemia.

B-lymphoid/myeloid stem cell origin in Ph-positive acute leukemia with myeloid markers

We report two cases of Philadelphia chromosome (Ph)-positive acute leukemia with definite myeloid markers. Ph was the sole chromosomal abnormality at presentation, and neither eosinophilia, basophilia, thrombocytosis nor hepatosplenomegaly was present. In both cases, Ph+ myeloblasts showed positive stain for myeloperoxidase and naphthol ASD chloroacetate esterase, which fulfilled the FAB criteria of acute myelogenous leukemia (AML). Ph+ myeloblasts co-expressed myeloid and B-lymphoid antigens (CD10, CD13, CD19 and CD33). In case 1, myeloblasts rearranged M-BCR, and the expression of M-BCR/ABL chimeric RNA was demonstrated by using the reverse transcription polymerase chain reaction (RT-PCR). They also clonally rearranged IGH. Ph clone disappeared on cytogenetic analysis in remission, and granulocytes in remission did not have rearranged M-BCR. In case 2, morphocytochemically distinct myeloid and lymphoid blast populations were seen. Myeloblasts and lymphoblasts were enriched > 96% as CD19-/CD33+ and CD19+/CD33- populations, respectively. Both of them possessed the identical rearrangement of IGH and M-BCR, indicating a common leukemic progenitor cell origin. Furthermore, m-BCR/ABL was detected in addition to M-BCR/ABL on RT-PCR. Accordingly, both cases were diagnosed as de novo Ph+ acute leukemia rather than as chronic myelogenous leukemia in blastic crisis. Their mixed B-lymphoid/myeloid characteristics strongly suggest that so-called 'Ph+ AML' is derived from Ph+ myeloid/B-lymphoid stem cells.

CD7+ stem cell leukemia/lymphoma. Features of a subgroup without circulating blast cells

Recent advances in immunology have clarified the cellular origin of hematopoietic neoplasms. Blast cells with a CD7+ CD4- CD8- phenotype are demonstrated to originate from malignant pluripotent hematopoietic stem cells. In this article, the authors describe three rare cases, designated as a lymphoma type of CD7+ stem cell leukemia/lymphoma, with clinical features described below. All three patients were admitted with non-Hodgkin lymphoma with a 2-month to 4-month history of lymphadenopathy. Histologic examination of lymph nodes showed lymphoblastic lymphoma (LBL) in all patients. Bone marrow blast cells had an immunophenotype consistent with CD7+ CD4- CD8- acute leukemia, although abnormal cells were not observed in the peripheral blood during the course of the disease. One patient had a recurrence in the bone marrow, with myeloperoxidase-positive blast cells expressing myeloid differentiation antigens. Chromosomal analysis detected a common abnormal karyotype initially and at relapse. Furthermore, the same T-cell receptor gene rearrangement was found initially and at relapse, suggesting that these blast cells originated from the same pluripotent leukemic clone. Additional studies on more patients are required to determine the clinical significance of this group, including the difference from CD7+ stem cell leukemia/lymphoma with circulating blast cells (leukemic type) or LBL.

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.

Flow cytometric analysis of lymphomas and acute leukemias

In summary, flow cytometry is highly applicable to the detection and classification of leukemias and lymphomas due to the ease with which single-cell suspensions may be made. Composite immunophenotypic analysis is essential for classifying leukemias once the disease is detected by traditional means. In contrast, in the detection of lymphoproliferative diseases, the composite immunophenotype is itself diagnostic of the disease process. Characterization of size, as measured by light scatter and by DNA ploidy and cell cycle analysis, contributes to the further subdivision of lymphoproliferative disorders. Specifically, small, monoclonal cells that are diploid with a synthetic fraction of 5% are characteristic of low-grade lymphomas. Admixtures of large and small cells wherein the large cells are monoclonal and the small cells are either monoclonal or heterogeneous may be seen in intermediate lymphomas. In this category, DNA ploidy is variable and the total synthetic fraction is usually between 5% and 15%. High-grade lymphomas, with the exception of the immunoblastic category, are usually of intermediate size, are diploid or near-diploid, and exhibit synthetic fractions greater than 15%. Interestingly, few reactive T cells are seen. Ongoing efforts to standardize procedures will eventually result in more widespread applicability together with improved understanding of the attributes and limitations of this technology. The most important consideration, however, is that the technology is useless in the absence of a working knowledge of the biology of the diseases to be characterized. Conversely, the complexity of flow cytometry is sufficient to warrant rigorous training of laboratory professionals in this field.

Clinical review on features and cytogenetic patterns in adult acute myeloid leukemia with lymphoid markers

Cytogenetic patterns in correlation with cytologic, biomolecular and clinical findings were studied in 45 adult patients with AML expressing at least one of the following lymphoid associated markers (LM): CD2, CD7, CD10, CD19, CD22, TdT. Four cytogenetic groups were recognized: group I, including 8 patients with 11q23 rearrangements; group II including 5 patients with the Ph chromosome; group III, with 19 patients and aberrations of the "myeloid type" including 4 cases with aberrations of chromosome 13, 3 cases with 1q and 7q anomalies, 2 cases with trisomy 11q; group IV, including 13 patients with normal karyotype. Patients showing extensive lineage infidelity were encountered more frequently in cytogenetic groups I and II than in groups III and IV. Two of 4 cases with aberrations of chromosome 13 showed two or more lymphoid features either at immunophenotyping or at biomolecular analysis of the configuration of lg and TCR genes. Patients with 11q23 rearrangements and with the Ph chromosome were generally young, presented with high WBC count and had low complete remission rate. Survival in Ph chromosome positive patients was uniformly short. We conclude that, although there is no cytogenetic anomaly specific for AML with LM, chromosome findings may be clinically relevant in AML with LM. A morphologic, immunologic and cytogenetic classification of AML with LM may constitute a working basis for future studies aimed at a better definition of clinicopathological features and optimal treatment strategy for these leukemias.

Phenotypic and molecular analysis of Ph1-chromosome-positive acute lymphoblastic leukemia cell lines

We have established 2 Philadelphia chromosome (Ph1)-positive acute lymphoblastic leukemia (ALL) cell lines, designated PALL-1 and PALL-2, from distinct adult Ph1-positive ALL patients. PALL-1 was established in nude mice, and PALL-2 was established in culture. Both retained the Ph1 chromosome and expressed the ALL type bcr/abl chimeric mRNA containing the junction of the first exon of BCR gene (e1) and second exon of c-abl gene (a2). PALL-1 and PALL-2 expressed CD34 surface antigen which is characteristic of early hematopoietic progenitor cells. PALL-2 expressed antigens for both pre-B and early myeloid cells and had rearrangements of both the heavy chain of immunoglobulin gene and the beta chain of T-cell-receptor gene. Both PALL-1 and PALL-2 expressed detectable levels of p53 gene RNA. Polymerase-chain-reaction-single-strand conformation polymorphism (PCR-SSCP) analysis of the p53 gene showed a normal pattern of mobility in both cell lines. Taken together, the 2 cell lines had features of Ph1-positive ALL: (i) hematopoietic progenitor cells with pre-B-cell phenotype and, (ii) activation of e1-a2 type bcr/abl oncogene without alterations of p53 gene. These unique lines should provide a valuable tool for studying the pathogenesis of Ph1-positive ALL.