Translocation (6;9)(p23;q34) in smoldering leukemia and acute nonlymphocytic leukemia

Chromosomal rearrangements in childhood acute myeloid leukemia and myelodysplastic syndromes

Recurrent chromosomal abnormalities present in the malignant cells of children with acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS) often correlate closely with specific clinical and biologic characteristics of the disease. Certain unique cytogenetic rearrangements are associated with distinct morphologic leukemic subtypes. These rearrangements should be detectable in most children with AML and MDS with the use of complementary molecular techniques such as fluorescence in situ hybridization (FISH), Southern blotting, and polymerase chain reaction. Apart from the diagnostic assessment, cytogenetic findings sometimes predict clinical outcome and thus also serve as prognostic parameters, which may affect the therapeutic decision. Alternative classifications of AML that take into account the genetic information are being proposed. Cytogenetic and molecular analyses may allow clinicians to more appropriately direct types of treatment. Abnormal fusion transcripts and chimeric proteins derived from karyotypic abnormalities now are being also targeted by novel therapeutic approaches.

Case of acute monocytic leukemia with 47,XY,+X,t(2;10)(q21.1;q26.1) and basophilia

The clinical cytogenetic findings of a patient with acute monocytic leukemia with peripheral and bone marrow basophilia are presented. The cytogenetic analysis of bone marrow cells established a pathologic clone with the following unusual karyotype: 47,XY,+X,t(2;10)(q21.1;q26.1). This chromosome abnormality has not been reported previously in leukemic diseases.

Acute myeloblastic leukemia with a pericentric inversion of chromosome 6 in a child with Down syndrome

Cytogenetic analysis of bone marrow cells demonstrated a pericentric inversion of chromosome 6 when acute myeloblastic leukemia (AML) was diagnosed in a 15-month-old child with Down syndrome. The abnormal clone with inv(6)(p24q16) was associated with FAB-M1 AML and disappeared when a complete remission was achieved. This is a unique cytogenetic abnormality for FAB-M1 AML in a child with Down syndrome and, to our knowledge, is only the second case of a pericentric inversion of chromosome 6 reported in AML.

Anaplastic large cell lymphoma of true histiocytic origin in an infant: unusual clinical, hematological, and cytogenetic features

We report here the case of a 7-month-old boy who developed anaplastic large cell lymphoma of true histiocytic origin or malignant histiocytosis, with fever, bone and bone marrow infiltration. Usual clinical features were absent. The neoplastic nature of the disease was supported by the presence of clonal chromosomal abnormalities [t(6;8)(p23;p21),der(8)del(8)(q11aq13), der(22) t(11;22) (q13;13)]. Neither B nor T lineage could be demonstrated here. Morphology, ultrastructural analysis, surface antigens expression, and cytogenetics were more specific for the monocyte-macrophage lineage.

Translocation t(6;9) in acute non-lymphocytic leukaemia results in the formation of a DEK-CAN fusion gene

The t(6;9) that characterizes a specific subtype of ANLL fuses the 3' part of a gene located on chromosome 9q34, CAN, to the 5' part of a gene located on chromosome 6p23, DEK. On the 6p- chromosome, the resulting DEK-CAN fusion gene is transcribed into a leukaemia-specific 5.5 kb chimaeric mRNA that encodes a putative DEK-CAN fusion protein. No transcription could be detected from the reciprocal CAN-DEK fusion on chromosome 9q+. Analysis of 17 t(6;9) ANLL cases showed that the translocation breakpoints occur in a single intron of 7.5 kb in the CAN gene (ICB9) and in a single intron of 9 kb in the DEK gene (ICB6). As a result, the presence of a t(6;9) in blood or bone marrow cells can be faithfully diagnosed by Southern blotting. Moreover, the result of the translocation is an invariable DEK-CAN transcript, which can be sensitively monitored by RNA-PCR. Surprisingly, a SET-CAN fusion gene was found in leukaemic cells from a patient with AUL. Like CAN, SET is located on chromosome 9q34, which explains the apparently normal karyotype of the leukaemic cells. The occurrence of a SET-CAN fusion gene indicates that CAN may be the relevant oncogene involved in leukaemogenesis, and that activation of CAN can be effectuated through fusion of its 3' part to either DEK or SET. As yet, the function of CAN, DEK or SET is unknown. None of the proteins shows consistent homology to any known protein sequences. However, preliminary localization data and analysis of sequence motifs suggested that DEK-CAN may have a role in transcription regulation. CAN contains several dimerization domains and a repeated motif that can function as an ancillary DNA-binding domain. DEK and SET are non-related proteins, but they share a stretch of acidic amino acids, which is also present in the fusion proteins.

Translocation t(6;9) occurring in acute myelofibrosis, myelodysplastic syndrome, and acute nonlymphocytic leukemia suggests multipotent stem cell involvement

The cytological and cytogenetic features of six patients with myeloid neoplasia and t(6;9)(p23;q34) including a case of acute myelofibrosis (AMF), a refractory anemia with excess of blasts (RAEB), and four cases of acute nonlymphocytic leukemia (ANLL) are described. Two patients in this series, both affected by ANLL type M2, presented an increase of bone marrow basophils, suggesting that this cytological-cytogenetic association is not absolute and that it may be more frequently observed in ANLL with maturation. All patients with de novo ANLL showed associated myelodysplastic features, and one patient presented a dysmyelopoietic syndrome, later evolving into ANLL. The presence of the t(6;9) in a range of myeloid neoplasias, with either concurrent myelodysplastic features or a preleukemic phase in cases of ANLL, provide evidence that this chromosome aberration may always involve a multipotent myeloid stem cell. Data on toxic exposure of the patients suggests that myeloproliferative disorders with the t(6;9) may frequently represent environmentally induced neoplasias.

Basophils in acute myeloid leukaemia

Thirty four out of 750 patients entered into the Medical Research Council's (MRC) 9th Acute Myeloid Leukaemia Trial had more than 1% basophils (range 1-27%) often with bizarre granulation and primitive forms, a rare finding in this disease. Both normal and abnormal karyotypes were present including abnormalities of 6p, 12p, and the Philadelphia chromosome. Basophilia was found in both "monolineage" and "multilineage" leukaemias and the commonest French-American-British (FAB) classification group was M2, followed by M4. Basophilia did not seem to be associated with a worse prognosis, although cases with abnormalities of 6p died of disease that was resistant to first line conventional chemotherapy.

Loss of the Y chromosome associated with translocation t(6;9)(p23;q34) in a patient with acute nonlymphocytic leukemia

A 34-year-old male with acute nonlymphocytic leukemia (ANLL) and a t(6;9)(p23;q34) is described, in whom loss of the Y chromosome had occurred in the t(6;9) clone. The leukemic blasts were relatively undifferentiated and there was no increase in marrow basophils. The unusual clonal evolution and hematologic features in this patient are compared to 27 previously documented cases with this translocation.

t(6;9) in bone marrow cells in two patients with sarcoidosis and acute myeloid leukemia

A t(6;9) was seen in bone marrow aspirates from two patients with sarcoidosis who developed acute myeloid leukemia. This is a new observation not previously reported.