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Einstein (São Paulo)

Print version ISSN 1679-4508On-line version ISSN 2317-6385

Einstein (São Paulo) vol.9 no.2 São Paulo Apr./June 2011

https://doi.org/10.1590/s1679-45082011ao2041 

Original Article

Molecular and cytogenetic abnormalities in acute myeloid leukemia: review and case studies

Elvira Deolinda Rodrigues Pereira Velloso1 

Carlos Henrique Ares Silveira da Motta2 

Juliana Braga Furtado2 

Nydia Strachman Bacal3 

Paulo Augusto Achucarro Silveira1 

Cynthia Bachir Moyses4 

Roberta Sitnik4 

João Renato Rebello Pinho4 

1Hematology, Department of Clinical Pathology, Hospital Israelita Albert Einstein – HIAE, São Paulo (SP), Brazil

2Graduate Program in Citogenetics and Molecular Biology, Special Techniques laboratory (lATE), Hospital Israelita Albert Eisntein – HIAE - São Paulo (SP), Brazil

3Division of Flow Cytometry, Department of Clinical Pathology, Hospital Israelita Albert Einstein – HIAE, São Paulo (SP), Brazil

4Special Technical laboratory (lATE), Hospital Israelita Albert Eisntein – HIAE - São Paulo (SP), Brazil


ABSTRACT

Objective:

To study the frequency of mutations that may lead to a good or bad prognosis, as well as their relation with the karyotype and immunophenotype in patients with acute myeloid leukemia.

Methods:

Thirty samples of patients with acute myeloid leukemia were studied, in which FLT3-ITD, FLT3-TKD and NPM1 mutations were investigated. All samples were submitted to immunophenotyping and 25 to karyotyping.

Results:

An occurrence of 33.3% NPM1 mutation and an equal number of FLT3-ITD mutation were observed. When only the cases with normal karyotype were studied, this figures increased to 50 and 40%, respectively. Eight percent of cases with normal karyotype and genotype NPM1+/FLT3- were included in the group of acute myeloid leukemia with good prognosis. The typical phenotype of acute myeloid leukemia with normal karyotype and mutated NPM1 (HLA-DR and CD34 negative) was not observed in this small series.

Conclusion:

Good prognosis cases were identified in this series, emphasizing the need to include new genetic markers in the diagnostic routine for the correct classification of acute myeloid leukemia, to more properly estimate prognosis and determine treatment.

Key words: Leukemia, myeloid, acute/genetics; Cytogenetics; Genetic makers; Chromosome aberrations

RESUMO

objetivo:

Estudar a frequência de mutações, que podem configurar bom ou mau prognóstico, bem como sua relação com estudo de cariótipo e imunofenotípico, em portadores de leucemias mieloides agudas.

Métodos:

Foram estudadas 30 amostras de portadores de leucemias mieloides agudas, que foram submetidas à pesquisa das mutações FLT3-ITD, FLT3-TKD e NPM1. Todas as amostras foram submetidas a estudo imunofenotípico e 25 delas foram submetidas a estudo cariotípico.

Resultados:

Pudemos observar frequência de 33,3% de mutação NPM1 e igual número em FLT3-ITD, frequência que se elevou para 50 e 40% quando se estudaram apenas os casos com cariótipo normal. Dos casos com cariótipo normal, 8% apresentaram o genótipo NPM1+/FLT3-, migrando para o grupo de leucemia mieloide aguda de bom prognóstico. Não observamos o fenótipo típico das leucemias mieloides agudas com cariótipo normal e NPM1 mutado (HLA-DR e CD34 negativos) nesta pequena casuística.

Conclusão:

O presente estudo foi capaz de identificar casos de bom prognóstico, enfatizando que há necessidade de se incorporarem à rotina diagnóstica novos marcadores genéticos, para a correta estratificação prognóstica e orientação terapêutica das leucemia mieloide aguda.

Descritores: Leucemia mieloide aguda/genética; Citogenética; Marcadores genéticos; Aberrações cromossômicas

INTRODUCTION

Acute myeloid leukemia (AML) is a heterogeneous group of neoplastic diseases with a large variability in regard to the clinical course and response to treatment, as well as in their genetic and molecular basis (more than 300 chromosomal translocations and genetic mutations have been described). More than one mutagenic event is probably necessary to give origin to the disease, encompassing cell proliferation mechanisms (class I mutations, such as BCR-ABL, FLT3, RAS, c-Kit, PTPN11, NF1, TEL-PDGRß ) and differentiation block (class II mutations, such as CBFßMYH11, AML1-ETO, TEL-AML1, PML-RARA, MLL, NUP98-HOXA9, PU.1, C/CEP α, AML1, AML-AMP19, CEBPA, NPM1 )(1,2).

In addition to age, cytogenetic and molecular changes present upon diagnosis are the main variables associated to AML prognosis. Until five years ago, cytogenetic abnormalities defined three risk groups for AML patients younger than 60 years. Approximately 25% of patients belonged to the low risk group, with t(15;17), t(8;21) and inv(16); 25 to 30% of the unfavorable risk, with the following gene rearrangement: MLL, t(6;9), t(9;22), monosomy/ deletions of chromosomes 5 and 7, inv(3)(q21q26) and complex karyotypes. Finally, 50 to 60% of patients had intermediate risk with t(9;11), +8, -Y and normal karyotype, the latter accounting for up to 50% of the cases(35). The estimated five-year survival for those with cytogenetic subtypes for low, intermediate and high risk was 55, 38 and 11%, respectively, in a series of 609 AML patients aged under 60 years(4).

Elderly patients traditionally have a higher percentage of cytogenetic abnormalities related to bad prognosis (up to 51%) and a lower percentage of good prognosis (about 4%)(6). There is a drop in the survival curves of those aged over 60 years for the same cytogenetic subtype, with the exception of acute promyelocytic leukemia (APL), according to a study of 1225 AML patients (5). Farag et al. also demonstrated that for the population older than 60 and treated with classic chemotherapeutic regimens, only 6% were alive after 5 years(7,8).

In the last few years, many genetic abnormalities were discovered in normal karyotype AML, especially mutations in the NPM1 (nucleophosmin), FLT3 (fmsrelated tyrosine kinase 3); CEPBA (CCAAT/enhancer binding protein α); MLL PTD (myeloid-lymphoid or mixed-lineage leukemia), NRAS -(neuroblastoma RAS viral oncogen), BAALC (brain and acute leukemia gene), ERG (v-ets erythroblastosis virus E26 oncogene-like) genes, among others(9). Approximately 45% of AML cases have normal karyotype; in that, the mutations of NPM1 and FLT3 genes are the most prevalent, corresponding to 45 to 55% and 35 to 45% of the cases, respectively(10).

FLT3 gene, in chromosome 13q12, encodes a receptor with tyrosine-kinase activity related to the activation of the cell proliferation signaling pathways, which is intensely expressed in the initial phases of myeloid precursor cells. Mutations like FLT3-ITD consist of in-tandem insertions of variable length in the region that encodes the receptor juxtamembrane domain. On the other hand, the FLT3-TKD mutation is punctual and affects the tyrosine-kinase domain. Both result in constant tyrosine-kinase activity. FLT3-ITD mutation appears in 35 to 45% of AML cases with normal karyotype, while the FLT3-TKD mutation is found in less than 5%(10).

The NPM1 gene, in chromosome 5q35, encodes a nucleolar phosphoprotein that makes the transportation between nucleus and cytoplasm, and is directly involved in the regulation and stability of nuclear proteins. The most frequent mutation is the duplication of four pairs of bases in exon 12 (85% of cases), but other types of insertion of four pairs of bases can also occur in the same region. This mutation causes the aberrant location of protein NPM1 in cytoplasm(11).

It has been demonstrated that normal karyotype AML with mutation in the NPM1 and CEBPA genes or in both have favorable prognosis, whilst mutations in gene FLT3 bear unfavorable prognosis. The cases with simultaneous mutations in genes FLT3 and NPM1 correlate to intermediate prognosis(12).

Based on such knowledge, the World Health Organization (WHO), in 2008, classified AML into different groups, including AML with recurrent genetic abnormalities that comprise nine subtypes, two of them being temporary entities (Chart 1)(13,14).

chart 1 Classification of the World Health Organization, 2008, for acute myeloid leukemias. 

AMl with recurrent genetic abnormalities
AMl with t(8;21)(q22;q22)- RUNX1T1-RUNX1
AMl with inv(16)(p13.1q22) or t(16;16)(p13.1;q22)- CBFß-MYH11
Acute promyelocitic leukemia with t(15;17)(q22;q21)- PML-RARA
AMl with t(9;11)(p22;q23)- MLLT3-MLL
AMl with t(6;9)(p23;q34)- DEK-NUP214
AMl with inv(3)(q21;q26.2) or t(3;3)(q21;q26.3) RPN1-EVI1
AMl (megakaryoblastic) with t(1;22)(p13;q13)- RBM15-MKL1
AMl with NPM1 mutation – temporary entity
AMl with CEBPA mutation - temporary entity
AMl with alterations related to myelodysplasia
Myeloid neoplasms related to therapy
Non specified AMl
Myeloid sarcoma
Myeloid proliferations related to Down syndrome
Blastic plasmacytoid dendritic cell neoplasm

AMl: acute myeloid leukemia.

Therefore, new groups of genetic risk have been recently defined for AML, as depicted in chart 2.

chart 2 Classification of acute myeloid leukemia, in 2010, per cytogenetic and molecular subtype (14). 

Favorable t(15;17)(q22;q21)-PML-RARA
t(8;21)(q22;q22)-RUNX1T1-RUNX1
inv(16)(p13.1q22) or t(16;16)(p13.1;q22)-CBFß-MYH11
Mutated NPM1 and with no FLT3-ITD (normal karyotype)
Mutated CEBPA (normal karyotype)
Intermediate I Mutated NPM1 and with FLT3-ITD (normal karyotype)
Wild-type NPM1 and with FLT3-ITD (normal karyotype)
Wild-type NPM1 and with no FLT3-ITD (normal karyotype)
Intermediate II t(9;11)(p22;q23)-MLLT3-MLL
Unfavorable or favorable cytogenetic abnormalities
Unfavorable inv(3)(q21;q26.2) or t(3;3)(q21;q26.3) -RPN1-EVI1
t(6;9)(p23;q34)-DEK-NUP214
t(v;11)(v;q23)-MLL rearrangement
-5/5q-, –7/7q
Complex karyotype

Other genetic abnormalities not listed in chart 2 also seem to predict survival. Mutations in c-Kit gene seem to be associated to a worse prognosis in AML with t(8;21) or inv(16), also called CBF-AML (core binding factor)(2,15). Monosomic karyotype, defined as the karyotype with two or more autosomal monosomies or one autosomal monosomy associated to the structural anomaly, has also been associated to the worst risk group(16,17).

Multiparametric flow cytometry is essential to characterize myeloid neoplasias and analyze a large number of cells in a short period of time, characterizing many antigens per cell. The identification of leukocyte differentiation antigens in the membrane and cytoplasm, allows for the detection of mixed, aberrant phenotypes, and the follow-up of minimal residual disease. The expression of certain antigens, such as CD7, CD11b, CD14, CD56 and CD34 may be associated to adverse prognosis. Aberrant phenotypes are found in at least 75% of AML(13). Immunophenotyping demonstrated peculiar features for AML with mutated NPM1, that is, antigen expression of CD13, CD33 and MPO concurrent with the expression of monocytic antigenes CD14 and CD11b, and the absence of the expression of CD34(13).

OBJECTIVE

To study the rate of mutations that may be associated to a good or bad prognosis, as well as their relation to karyotype and immunophenotype studies in patients with AML.

METHODS

The Special Technique Laboratory of the Hospital Israelita Albert Einstein (HIAE) receives samples of AML patients from different treatment centers for immunophenotyping, cytogenetic and molecular studies. As from 2009, after signing the informed consent, 30 bone marrow samples from newly diagnosed or relapsed AML patients were submitted to study of FLT3-ITD, FLT3-TKD and NPM1 mutations. All samples were submitted to immunophenotypic study and 25 of them to kariotyping.

The immunophenotyping study was performed using cells labeled with monoclonal antibodies for proliferative panel (CD2, CD4, CD7, CD10, CD11b, CD11c, CD13, CD14, CD15, CD19, CD20, CD22, CD33, CD38, CD34, CD56, CD64, CD71, CD117, HLA-DR, glycophorin A, CD3 c, MPOc, TdT and CD79a). After preparing with ammonium chloride (hemolytic buffer), flow cytometry was performed (Epics XL-MCL or FC-500 – Beckman Coulter).

Cytogenetic study was carried out in 24- and 48-hour cultures, with no stimulating agents, submitted to G-banding and described according to the international nomenclature (ISCN 2009).

For analysis of the mutations in FLT3 and NPM1 genes, the DNA of the samples was extracted using the QIAmp DNA Blood Mini Kit (Quiagen), purified (EXOSAP) and submitted to PCR for amplification, using specific primers and labeled for the FLT3-ITD (exon 14/15) and NPM1 mutations. Capillary electrophoresis was utilized for analyses of FLT3-ITD and NPM1 per fragment size. To investigate FLT3-TKD mutations, a new PCR reaction was performed with specific primers for the Nested-PCR, followed by sequencing. The analysis of the FLT3-ITD and NPM1 mutations were performed by means of the software GeneMapper, and the sequencing, by SeqScape.

RESULTS

The description of the immunophenotypical, molecular, and karyotypicl findings is depicted on chart 3.

chart 3 List of patients analyzed with immunophenotypical results, mutations FLT3-ITD and NPM1, and karyotype. 

NUMBER SEX AGE NPM1 FLT3 KARIOTYPE Prognostic genetic Classification Lineage (CD) Maturation (CD) Immaturity Activation Proliferation Lineage B (CD) Lineage T/NK (CD)
ITD 13 33 117 MPO 11b 11c 15 14 15/64 4 34 TdT 38 HLA-DR 71 19 20 22 79a 2 7 56
1 FEM 65 POS POS 46,XX[20] intermedate-1 POS POS POS NEG POS NEG POS NEG - POS NEG NEG POS POS NEG NEG - - NEG POS POS NEG
2 FEM 34 POS POS 46,XX[20] intermediate-1 POS POS NEG - POS POS POS NEG - - NEG - POS NEG POS - - - - NEG NEG NEG
3 FEM 30 POS POS 46,XX[20] intermediate-1 POS POS POS POS NEG POS POS NEG - POS NEG - POS POS POS NEG - - NEG NEG NEG NEG
4 MALE 30 POS NEG 46,XY[20] favorable POS POS POS POS NEG POS POS NEG - POS NEG - POS NEG POS NEG - - NEG NEG NEG NEG
5 FEM 4B POS NEG 46,XY[20] favorable POS POS POS POS NEG POS POS NEG - NEG POS - POS POS NEG NEG - - NEG NEG POS NEG
6 FEM 72 NEG POS 46,XX[20] intermediate-1 POS POS POS POS - POS POS NEG - NEG POS - POS POS POS NEG - - NEG NEG NEG NEG
7 FEM 57 NEG NEG 46,XX[20] intermediate-1 POS POS POS POS NEG POS POS NEG - NEG POS - POS POS POS - - - NEG NEG NEG NEG
8 FEM 32 NEG NEG 46,XX[20] intermediate-1 POS POS POS POS POS POS POS NEG - POS NEG - POS POS POS NEG - - NEG NEG NEG NEG
9 MALE 73 NEG NEG 46,XY[20] intermediate-1 POS POS POS POS POS NEG POS NEG - POS NEG - POS POS POS NEG - - NEG NEG POS NEG
10 FEM 44 NEG NEG 46,XX, inv (9) (p12q13)[20] intermediate-1 (normal varient) POS POS POS POS NEG NEG NEG NEG - NEG POS NEG POS NEG POS NEG - - NEG NEG NEG NEG
11 FEM 30 NEG POS 46,XX, t(15;17)(q22;q21) [14] favorable (LPA) POS POS POS POS NEG NEG POS NEG - NEG POS NEG POS NEG POS NEG - - NEG POS NEG NEG
12 FEM 11 NEG POS 46,XX,t(15;17)(q22;q21)[16]/46,XX[4] favorable (LPA) POS POS POS POS NEG NEG NEG NEG - NEG NEG - FOG- NEG POS POS NEG NEG NEG NEG NEG NEG
13 FEM 30 NEG NEG 46,XX,t(15;17)(q22;q21)[7],46,XX[13] favorable (LPA) POS POS POS POS NEG NEG NEG NEG - NEG NEG - POS NEG NEG NEG - - NEG NEG NEG NEG
14 FEM 27 NEG NEG 46,XX,t(15;17)(q22;q21) [20] favorable (LPA) POS POS POS POS NEG NEG NEG NEG - NEG NEG - POS NEG NEG NEG - - NEG NEG NEG NEG
15 FEM 66 NEG NEG 46,X,del(X)(q24),t(4;21;8)(q21;q22;q22)[21] favorable (varient (8;21)) NEG POS POS NEG NEG POS POS NEG - POS NEG - POS POS NEG NEG - - NEG NEG NEG POS
16 MALE 11 NEG NEG 46,XY, del(16)(q22)[20] intermediate-2 POS POS POS POS NEG NEG NEG NEG - NEG POS - POS POS- POS NEG - - NEG NEG NEG NEG
17 FEM B NEG NEG 46,XX, add(2)(q37)[20] inetrmediate-2 POS POS POS POS NEG NEG NEG NEG - NEG POS - POS POS NEG NEG - - NEG NEG NEG POS
18 MALE 59 NEG NEG 46,XY,del(3)(p21)[18] inetrmadiate-2 NEG POS NEG - NEG NEG NEG NEG - NEG NEG - POS NEG POS NEG - - - POS POS NEG
19 FEM 48 POS POS 47,XX,+5[3]/46,XX[17] intermadiate-2 POS POS POS POS NEG NEG NEG NEG - POS POS - POS POS POS NEG - - NEG NEG NEG NEG
20 FEM 68 NEG NEG 46,XX,t(6;19)(q 16;p 12) [5]/46,X[15] intermadiate-2 POS POS POS NEG NEG POS NEG NEG - NEG NEG - POS POS POS NEG - - NEG NEG POS NEG
21 MALE 61 NEG NEG 46,XY,t(3;3)(q21;q26)[19]/46,XY[1] unfavorable POS POS POS NEG POS NEG NEG NEG - NEG POS POS POS POS POS NEG - - NEG NEG POS NEG
22 MALE 15 NEG NEG 46,XY,t(6;9)(p23;q34)[20] 46,XY, inv(9) unfavorable POS POS NEG - POS POS POS NEG - POS NEG - POS POS NEG NEG - - - NEG NEG NEG
23 MALE 9 NEG NEG p21q13), t(11;?)(q23;?) [19] unfavorable POS POS POS NEG NEG NEG NEG NEG - NEG POS - POS POS POS NEG - - NEG NEG NEG NEG
24 FEM 61 NEG NEG 46,XX,del(7)(q21)[7]/46,XX[13] unfavorable POS POS POS POS NEG NEG NEG NEG - POS POS - POS NEG NEG NEG - - NEG NEG NEG POS
25 MALE 20 NEG NEG 46,XY,t(9;18)(q34;q22),t(13;20)(q12;q13.2)[15]/46,XY[5] unfavorable POS POS POS - - POS POS NEG - POS POS - POS POS POS NEG - - - NEG NEG POS
26 MALE 61 POS POS - POS POS NEG POS NEG NEG NEG NEG - NEG NEG - NEG NEG NEG NEG - - NEG NEG NEG POS
27 FEM 89 POS POS - POS POS POS NEG NEG NEG NEG NEG - NEG POS - POS POS POS NEG - - NEG NEG POS NEG
28 FEM 51 POS NEG - POS POS POS POS POS POS POS NEG - POS NEG - POS POS POS NEG - - NEG NEG POS NEG
29 FEM 94 POS NEG - POS POS POS NEG NEG NEG NEG NEG - NEG POS - POS POS POS NEG - - NEG NEG POS NEG
30 FEM 61 NEG POS - POS POS POS POS - NEG POS NEG - NEG POS - POS POS POS NEG - - NEG NEG POS NEG

In the cases studied, NPM1 gene mutation was found in 10 out of 30 samples (33.3%), the same been observed for the FLT3-ITD mutation. The coexistence of both occurred in six cases. No sample was positive for the FLT3-TKD mutation.

Of the 25 samples with karyotypes analyzed, 10 had normal karyotypes (40%). When only normal karyotypes were analyzed, 50% presented the mutation in NPM1 gene and 40% FLT3-ITD mutation. The concurrent presence of both was diagnosed in 30% of the cases.

Among the 15 samples diagnosed with abnormal karyotype, 4 presented karyotypes with t(15;17) and one with the variant t(8;21), considered of good prognosis. Five samples presented karyotypes of unfavorable prognosis, t(3;3), t(6;9), del(7)(q21), 11q23 rearrangement and one complex. Five other cases considered of intermediate prognosis such as del(16)(q22), add(2)(q37), del(3)(p21), 5 trisomy and t(6;19) were also found.

Three cases of abnormal karyotypes also presented molecular alterations, two with t(15;17) and FLT3-ITD mutation, and one 5 trisomy with mutated FLT3-ITD and NPM1.

According to our study, of the 25 cases with karyotype study, 28% were classified as favorable prognosis, among which 8% had normal karyotype and mutated NPM1, and 20% had abnormal karyotype (16% t(15;17), and 4% t(8;21). Thirty-two percent were classified as intermediate-1, all with normal karyotype and 12% mutated NPM1 and FLT3-ITD, 4% FLT3-ITD and 16% wild for both mutations. The remaining cases, all with abnormal karyotype, were stratified as intermediate-2 (20%) and unfavorable (20%) (Figure 1).

Figure 1 Frequency of prognosis as per the classification of acute myeloid leukemias according to cytogenetic and molecular subtypes. 

The immunophenotype study demonstrated that 18 cases (60%) expressed non-myeloid lineage-associated antigens: CD7 in 10 cases, CD56 in 5 cases and CD11b in 7 cases; in that, four cases having concurrence of CD7 and CD11b. The expression of CD56 was detected in 16.6% of AML cases and 20% of cases with FLT3 mutation.

The immunophenotype study of four cases with wildtype NPM1 and FLT3 mutation (2 with normal karyotype and 2 with no karyotype study) demonstrated, in two of them, absence of CD34 expression. Of the 6 cases with mutated NPM1 and FLT3-ITD genotype (3 with normal karyotype, 1 abnormal, 2 with no karyotype study), four had no expression of CD34. Only one of 4 cases of wildtype FLT3-ITD and NPM1 (1 with normal karyotype, 2 with t(15;17) and 1 with no karyotype study) had absent CD34 expression.

DISCUSSION

Although a small number of samples from AML patients was studied, the rates observed for FLT3 and NPM1 mutations were similar to those found in the literature, for all subtypes of AML, as well as for AML with normal karyotypes.

In a publication with a national series, a total of 43.7% in NPM1 mutations were observed in AML subtype with normal karyotype, a rate similar to the one observed in the present study (18). The incidence of 33.3% FLT3-ITD mutation was slightly higher that reported by LucenaAraujo (23.6%), being found in the many subtypes of AML, including APL, these data being consonant to the international and national literature(18,19).

Mutation type TKD was not detected, corroborating the less prevalent finding of this mutation in Brazilian series when compared to American or European ones(1820).

In regard to immunophenotype, the small series hindered comparison with data found in the literature, such as smaller expression of CD56 in the subtype with mutated FLT3 and absence of CD34 expression and HLA-DR in the AML with mutated NPM1. In this study, the rate of expression of CD56 was similar to the one observed in AML with FLT3 mutation and also one of the patients with NPM1+/FLT3- AML presented blast cells with the expression of CD34 and HLA-DR.

Considering the above, it may be inferred that the diagnostic routine should encompass new genetic markers for correct prognostic stratification and treatment option in AML.

CONCLUSION

The rate of FLT3 and NPM1 mutations found in this series was similar to that found in the literature, and it was possible to identify a subgroup with normal karyotype NPM1+/FLT3-, currently recognized as of good prognosis.

Study carried out at Special Technical Laboratory (LATE), Hospital Israelita Albert Einstein – HIAE, Sao Paulo (SP), Brazil.

ACKNOWLEDGEMENT

Molecular Biology Technical Team: Diogo P Marquezoni, Gregório TF Tastoli, Juliana NM Rodrigues, Letícia Oyakawa, Ozires PS Ramos, Roberta Sitnik, Roberta C Petroni, Rubia AF Santana, Vanessa FD Castro.

Cytogenetics Technical Team: Andréa BM Castro, Cláudia IEC Fabris, Cristina A Ratis, Daniel A Oliveira, Daniela Borri, Priscila F Fernandes, Renata C Elias, Renata K Kishimoto, Silvia HA Figueira.

Cytometry Technical Team: Ana Carolina Apelle, Rodolfo P Correia, Ruth H Kanayama, Sonia T Nozawa.

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Received: January 11, 2011; Accepted: May 10, 2011

Corresponding author: Elvira Deolinda Rodrigues Pereira Velloso – laboratório de Técnicas Especiais do Hospital Israelita Albert Einstein – Avenida Albert Einstein, 627/701 – Morumbi – CEP 05651-901 – São Paulo (SP), Brasil – Tel.: (11) 2151-5555 – Fax: (11) 2151-2122 – e-mail: elviradv@einstein.br

Conflict of interest: none

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