Molecular cytogenetic investigations in a novel complex variant of t(8;21)(q22;q22) with ins(15;21)(q15;q22.2q22.3) in a patient with AML-M2 subtype

Acute myeloid leukemia (AML) is a clinically and molecularly heterogeneous disease characterized by the aberrant proliferation of myeloid stem cells, reduced apoptosis and blockage in cellular differentiation. The present report describes the results of hematological, cytogenetic, and fluorescence in situ hybridization (FISH) analysis in a 25-year-old man diagnosed with AML-M2. Cytogenetic as well as FISH analysis revealed a complex translocation involving four chromosomes, with the karyotype 45,−Y,der(X)t(X;8)(p21;q22),der(8)t(8;21)(q22;q22),ins(15;21)(q15;q22.2q22.3),der(21)t(8;21)(q22;q22). The breakpoints at 8q22 and 21q22 suggested a rearrangement of the RUNX1T1 (alias ETO) and RUNX1 (previously AML1) genes, respectively. Using a dual-color FISH test with RUNX1T1 and RUNX1 probes, we demonstrated an RUNX1/RUNX1T1 fusion signal on the derivative chromosome 8, establishing this translocation as a novel complex variant of t(8;21)(q22;q22).     

Identification of ins(8;21) with AML1/ETO fusion in acute myelogenous leukemia M2 by molecular cytogenetics

A high percentage of cases of acute myelogenous leukemia (AML) of the M2 subtype show a rearrangement between the AML1 and ETO genes. The detection of the AML1/ETO fusion has clinical relevance because patients with this subtype have a good prognosis. We present the results of conventional and molecular cytogenetic studies in a patient with acute myelogenous leukemia French-American-British M2 classification, who had a complex karyotype involving chromosomes 8 and 21. Dual-color fluorescence in situ hybridization (FISH) using the AML1/ETO probe demonstrated a recombination of both genes on an add(8) chromosome. The use of other FISH probes (CEP8, c-myc and TEL21) and spectral karyotyping indicated that AML1/ETO fusion occurred as a consequence of a previously undescribed ins(8;21)(q22;q22.1q22.3).     

Molecular cytogenetic findings in a three-way novel variant of t(1;8;21)(p35;q22;q22): a unique relocation of the AML1/ETO fusion gene 1p35 in AML-M2

Acute myeloid leukemia (AML) is a malignant neoplasm of hematopoietic stem cells characterized by an abnormal proliferation of myeloid precursors, a reduced rate of apoptosis, and an arrest in cellular differentiation. The present report deals with the results of hematologic, immunophenotypic, cytogenetic, fluorescence in situ hybridization (FISH), and molecular analyses of a 53-year-old female patient diagnosed with AML-M2. Cytogenetic and FISH analysis revealed a complex translocation involving three chromosomes showing t(1;8;21)(p35;q22;q22). The observation of breakpoints at 8q22 and 21q22 suggests a rearrangement of the ETO and AML1 genes, respectively. Using a dual-color FISH test with ETO and AML1 probes, an AML1/ETO fusion signal on the derivative 1p35 instead of der(8) was demonstrated. To the best of our knowledge, this is the first report about the relocation of the AML1/ETO fusion gene to the 1p35 rather than der(8), suggesting the presence of a novel variant of t(8;21)(q22;q22) in the observed patient.     

Molecular characterization of AML with ins(21;8)(q22;q22q22) reveals similarity to t(8;21) AML

In acute myeloid leukemia (AML), nonrandom clonal chromosome aberrations are detectable in ～ 55% of adult cases. Translocation t(8;21)(q22;q22) resulting in the 5'RUNX1/3'RUNX1T1 fusion gene occurs in ～ 8% of AML cases. Also, ins(8;21) and ins(21;8) have been described that show a broad heterogeneity at the molecular level with inserted fragment sizes ranging from 2.4 to 44 Mb. Microarray-based comparative genomic hybridization (arrayCGH) in 49 intermediate-risk AML and RT-PCR-based screening in 532 AML cases allowed the detection of ins(21;8)/ins(8;21) in three cases; arrayCGH and subsequent RT-PCR revealed an ～ 0.5 Mb sized inserted fragment generating the 5'RUNX1/3'RUNX1T1 fusion gene in one case with a submicroscopic ins(21;8)(q22;q22q22) whereas the other two cases were identified by banding analysis and RT-PCR, respectively. Gene expression profiling (GEP) and a detailed review of the literature highlighted similar biological features of AML cases with ins(21;8)/ins(8;21) and t(8;21)(q22;q22). Our study demonstrates the potential of high-resolution array-based analysis and GEP and provides further evidence that AML with insertions generating the 5'RUNX1/3'RUNX1T1 fusion not only biologically resemble the t(8;21)(q22;q22) AML subgroup, but might also share its prognostically favorable clinical behavior. Thus, similar treatment options should be considered in these patients.     

An unusual three-way translocation t(21;8;1)(q22;q22;q32) in a case of acute myeloid leukemia (M2)

Variant forms of the classic translocation t(8;21) are uncommon and account approximately 3% of all t(8;21)(q22;q22) in acute myeloid leukemia (AML) patients. These forms involve chromosomes 8, 21, and other chromosomes. Here we report a Tunisian patient with a complex rearrangement t(21;8;1)(q22;q22;q32) revealed by conventional chromosomal study at diagnosis. Fluorescence in situ hybridization study revealed the presence of the AML1-ETO chimeric gene on the derivative chromosome 8. To the best of our knowledge, this is the second case of t(21;8;1) of AML-M2 reported in the literature with the involvement of the same breakpoint at 1q32. This illustrates that this complex translocation is rarely encountered in AML and reinforces the fact that this region may harbour a critical gene candidate that may play an important role in the pathogenesis of AML. More cases are needed to elucidate its clinical features and prognosis.     

Fluorescence in situ hybridization analysis of the cryptic t(12;21) (p13;q22) in childhood B-lineage acute lymphoblastic leukemia.

We evaluated retrospectively the cryptic t(12;21)(p13;q22) in 15 children with early B-lineage acute lymphocytic leukemia who had a normal karyotype by using the locus specific probes of TEL and AML1 genes in a dual color fluorescence in situ hybridization (FISH). The FISH analysis revealed six patients with the fusion gene TEL/AML1 on chromosome 21, three of whom possessed a double fusion gene. In addition, the AML1 probe revealed hyperdiploid clones that were not detected in the conventional cytogenetic analysis. A discrepancy between the proportion of cells with the fusion gene in interphase nuclei and metaphases was noted.     

Acute myeloid leukemia (AML) with t(8;21)(q22;q22) relapsing as AML with t(3;21)(q26;q22)

We here report on an 48-year-old male patient with a primary diagnosis of acute myeloid leukemia (AML)-M2 with t(8;21)(q22;q22), who developed complete hematologic and molecular remission after induction chemotherapy. Thirteen months later, he relapsed and showed an AML-M2 with t(3;21)(q26;q22). Retrospectively, polymerase chain reaction (PCR) for AML1-EVI1 and EVI1 overexpression was performed on bone marrow and peripheral blood samples taken at diagnosis and during the first year after the first manifestation of AML to quantify the AML1-EVI1-positive clone. In a bone marrow sample taken 25 days from diagnosis, PCR for AML1-EVI1 was negative, and EVI1 expression, as assessed by quantitative real-time PCR, was within the same range as that of healthy controls. These data suggest that this patient developed a secondary therapy-related AML rather than a relapse.     

Duplication 15q in a patient with t(8;21) acute myeloblastic leukemia (M2)

We present unique chromosomal abnormalities found in a patient with acute myeloblastic leukemia (AML) of French-American-British subtype M2. The patient was referred for an evaluation of chromosomal anomaly associated with AML. She was found to have an abnormal karyotype 46,XX,t(8;21)(q22;q22), and a questionable dup(15)(q15q22) in the majority of cells analyzed. Two cells had the same chromosomal anomalies plus a duplicated derivative chromosome 21 [der(21)t(8;21)(q22;q22)]. These cytogenetic findings were confirmed by fluorescence in situ hybridization utilizing the appropriate DNA probes. To our knowledge, this is the first case report of a combination of the translocation between chromosomes 8 and 21, a duplication of chromosome 15 [dup(15)(q15q22), and a duplicated derivative chromosome 21 [der(21)t(8;21)(q22;q22)].     

Novel chromosome 16 abnormality--der(16)del(16) (q13)t(16;21)(p11.2;q22)--associated with acute myeloid leukemia.

Inversion of chromosome 16 is a common feature of acute myeloid leukemia (AML) M4, while t(16;21), although also associated with AML, appears to be a separate entity. We present a patient with myelodysplastic syndrome (MDS) who transformed to AML-M1. The karyotype was normal at diagnosis; at 15 months, hematological evidence of transformation was present, and repeat cytogenetics showed a novel rearrangement of one chromosome 16. Two breaks had occurred; one in the short arm at 16p11, with translocation of the segment distal to this onto chromosome 21q, and the other in the long arm at 16q22 with subsequent deletion of the segment from 16q22-->qter. Fluorescence in situ hybridization (FISH) confirmed the abnormalities detected by cytogenetics and excluded involvement of the AML1 gene on 21q22. While the 16q22 breakpoint was at the usual site for the inv(16), the 16p11 was not. The patient is more characteristic of t(16;21) than inv(16), and adds to the spectrum of chromosome 16 abnormalities in AML.     

t(8;21)(q22;q22) in blast phase of chronic myelogenous leukemia

The blast phase of chronic myelogenous leukemia (CML) frequently is associated with cytogenetic evidence of clonal evolution, defined as chromosomal aberrations in addition to the t(9;22)(q34;q11.2). We identified the t(8;21)(q22;q22) and other cytogenetic abnormalities by conventional cytogenetics and fluorescence in situ hybridization in 2 patients with t(9;22)-positive CML at the time of blast phase. The t(8;21), which typically is associated with a distinct subtype of de novo acute myeloid leukemia (AML) carrying the aml1/eto fusion gene, was accompanied by increased bone marrow myeloblasts (33%) in case 1 and extramedullary myeloid sarcoma in case 2, suggesting its possible role in disease progression. In case 1, the leukemic cells in aspirate smears had salmon-colored cytoplasmic granules, and immunophenotypic studies showed that the blasts expressed CD19. These findings suggest that the pathologic features of blast phase CML with the t(8;21) resemble those of de novo AML with the t(8;21).     

A new variant t(6;15;17)(q25;q22;q21) in acute promyelocytic leukemia: fluorescence in situ hybridization confirmation

Acute promyelocytic leukemia (APL) is characterized by the t(15;17)(q22;q21), which results in the fusion of the promyelocytic leukemia (PML) gene at 15q22 with the retinoic acid alpha-receptor (RARalpha) at 17q21. The 2 chimeric genes PML/RARalpha and RARalpha/PML are thought to play a role in leukemogenesis. We report a case of APL in a patient carrying an apparently complex variant translocation identified as t(6;15;17) by R-banding and whole chromosome 15 and 17 painting. However, FISH analysis with a PML/RARalpha dual-color kit showed a more complex translocation, resulting presumably from a two-step rearrangement, with PML-RARalpha fusion gene located as expected on the der(15) but the residual 5'-RARalpha signal located on the der(6). The patient achieved complete remission with all-trans retinoic acid treatment associated with chemotherapy. This case illustrates the usefulness of combined cytogenetics, FISH, and molecular biology to evidence the PML/RARalpha fusion gene in complex cases.