Derivative (6)t(1;6)(q22;p21) revealed in bone marrow cells by FISH 9 months before diagnosis of acute T-lymphoblastic leukemia

New recurrent chromosome change in pediatric therapy-related myelodysplastic syndrome: unbalanced translocation 1/6 with cryptic duplication of short arm of chromosome 6

The incidence of therapy-related myelodysplastic syndrome (t-MDS) in pediatric patients is increasing in parallel with the more successful management of the primary tumor, but scant information is available on clinical and cytogenetic characteristics. We report here two children affected by t-MDS after chemo/radiotherapy for a primary solid tumor, both with an unbalanced translocation 1/6 in their bone marrow. Characterization by array comparative genomic hybridization of the imbalances showed an almost identical pattern: almost complete trisomy of the long arm of chromosome 1, and a terminal deletion and interstitial duplication of the short arm of chromosome 6. The gain of chromosome 6 short arm encompasses regions already highlighted as possibly relevant for t-MDS in adults, and we suggest that the unbalanced translocation reported here be considered a new recurrent, non-random chromosomal abnormality in pediatric patients with t-MDS.

Genomic gain at 6p21: a new cryptic molecular rearrangement in secondary myelodysplastic syndrome and acute myeloid leukemia

Fluorescence in situ hybridization and comparative genomic hybridization characterized 6p rearrangements in eight primary and in 10 secondary myeloid disorders (including one patient with Fanconi anemia) and found different molecular lesions in each group. In primary disorders, 6p abnormalities, isolated in six patients, were highly heterogeneous with different breakpoints along the 6p arm. Reciprocal translocations were found in seven. In the 10 patients with secondary acute myeloid leukemia/myelodysplastic syndrome (AML/MDS), the short arm of chromosome 6 was involved in unbalanced translocations in 7. The other three patients showed full or partial trisomy of the 6p arm, that is, i(6)(p10) (one patient) and dup(6)(p) (two patients). In 5/7 patients with unbalanced translocations, DNA sequences were overrepresented at band 6p21 as either cryptic duplications (three patients) or cryptic low-copy gains (two patients). In the eight patients with cytogenetic or cryptic 6p gains, we identified a common overrepresented region extending for 5-6 megabases from the TNF gene to the ETV-7 gene. 6p abnormalities were isolated karyotype changes in four patients. Consequently, in secondary AML/MDS, we hypothesize that 6p gains are major pathogenetic events arising from acquired and/or congenital genomic instability.

Three cases of near-tetraploid acute myeloid leukemias originating in pluripotent myeloid progenitors

We report three cases of acute myeloid leukemia (AML) with a near-tetraploid karyotype in most metaphases while lacking chromosomal abnormalities typical for AML. All patients, 63, 72 and 81 years old, were female. In two cases, AML was diagnosed 5-7 months after a cytopenic period while the third patient had a secondary AML after therapy for a pleural tumor. Leukemic blasts were classified as AML M0, AML M1 and AML without further specification. Two patients died on the 18th and 52nd day after the start of cytotoxic chemotherapy, the third patient refused chemotherapy and died 22 days after the diagnosis. The three patients may represent a distinct AML category with the following features: (1) the near-tetraploid karyotype in most bone marrow metaphases examined at diagnosis of AML; (2) the presence of very large myeloid blasts in the bone marrow and dysplastic changes in erythroid and/or megakaryocytic lineages pointing to the origin of AML in pluripotent myeloid progenitor cells; (3) the expression of the CD34 antigen; (4) the low growth of granulocyte-macrophage colony forming cells in culture; and (5) the presence of a preleukemic phase, a higher age and a poor prognosis.