Frequency, hematopathology, and detection of a new isodicentric variant of deletion 20q

Clinical and molecular cytogenetic studies in ten patients with hematological malignancies characterized by t(20;21)(q11;q11) resulted from del(20q)

This study reports 10 patients with hematological malignances with t(20;21)(q11;q11) resulting from del(20q) (for example, der(20)del(20)(q11q13)t(20;21)(q11;q11) and der(21)t(20;21)(q11;q11)) and described their clinical features and the possible prognostic significance of this abnormality. The t(20;21)(q11;q11) was a rare but recurrent abnormality secondary to del(20q) besides i(20q-). The frequency of der(20)del(20)(q11q13)t(20;21)(q11;q11) among our patients with del(20q) was 2.4%. It was considered that the 20q deletion preceded translocation with chromosome 21. This abnormality is often cryptic, occurs predominantly in older men and is observed most often in myelodysplastic syndromes. Patients with this abnormality have an unfavorable prognosis, similar to patients with i(20q-). The molecular consequences of der(20)del(20)(q11q13)t(20;21)(q11;q11) may be different from patients with i(20q-). To the best of our knowledge this is the largest dataset published to date.

Isolated deletion of the long arm of chromosome 20 [del(20q12)] in myelodysplastic syndrome: a case report and literature review

Isolated deletion of the long arm of chromosome 20 [del(20q12)] is a rare abnormality in patients with de novo myelodysplastic syndrome. It is characterised by refractory thrombocytopenia, minimal haematological dysplasia and a lower risk for progression to acute myeloid leukaemia. Its distinction from chronic autoimmune thrombocytopenia, although clinically and morphologically difficult, is critical. We report a case of refractory cytopenia and unilineage dysplasia in an elderly woman with isolated del(20q12), identified via fluorescence in situ hybridisation analysis of her bone marrow. In order to avoid a misdiagnosis, we suggest that cytogenetic analysis be performed on all patients suspected to have myelodysplastic syndrome with predominant thrombocytopenic presentation.

Morphology, cytogenetics, and survival in myelodysplasia with del(20q) or ider(20q): a multicenter study

Isochromosome of the long arm of chromosome 20 with interstitial loss of material [ider(20q)] is a rare cytogenetic abnormality reported in myelodysplastic syndrome (MDS), with neither specific morphological pattern nor clear prognostic significance. The aim of this retrospective multicentric study is to compare the peripheral blood and bone marrow morphology of MDS patients with ider(20q) (n = 13) and del(20q) (n = 21) and controls (n = 47) in order to investigate whether the ider(20q) harbors specific morphological features. The secondary objective is to compare the outcome of patients from both groups. This study performed on the largest cohort of MDS patients with ider(20q) is the first that identifies specific morphological features (hypogranulated and vacuolized neutrophils and neutrophil erythrophagocytosis) allowing the identification of this cytogenetic abnormality with high sensitivity (70%) and specificity (85.7%). Suspected ider(20q) by morphology should therefore support targeted FISH tests in case of non informative karyotype. This combined approach will allow a better estimation of the prevalence of this underdiagnozed entity. The overall survival and progression-free survival did not statistically differ in both groups. However, hypogranulated and vacuolized neutrophils were significantly associated with survival.

Characterization of chromosome arm 20q abnormalities in myeloid malignancies using genome-wide single nucleotide polymorphism array analysis

Deletion of the long arm of chromosome 20 is a common abnormality associated with myeloid malignancies. We characterized abnormalities of chromosome 20 as defined by metaphase cytogenetics (MC) in patients with myeloid neoplasms to define commonly deleted regions (CDR) and commonly retained regions (CRR) using genome-wide, high resolution single nucleotide polymorphism array (SNP-A) analysis. We reviewed the MC results of a cohort of 1,162 patients with myeloid malignancies, including myelodysplastic syndromes (MDS), MDS/myeloproliferative neoplasia (MDS/MPN), and acute myeloid leukemia (AML). We further analyzed a subcohort of 532 patients by SNP-A using the Affymetrix Genome-Wide Human SNP Array 6.0 and GeneChip Human Mapping 250K Nsp arrays. By MC, 5% (54/1,162) harbored a deletion of 20q; in 30% (16/54), del(20q) was the sole cytogenetic abnormality. By SNP-A analysis, we identified del(20q) in 23 patients, 3 not detected by MC. In four cases, monosomy 20 with a marker chromosome by MC was proven to be an interstitial deletion of 20q by SNP-A. We defined 2 CDR and 2 CRR on chromosome arm 20q: CDR1 spanned 2.5 Mb between bands 20q11.23 and 20q12, while CDR2 encompassed 1.8 Mb within 20q13.12. CRR1 spanned 1.9 Mb within 20q11.21 and CRR2 encompassed 2.5 Mb within 20q13.33. In contrast to other chromosomes frequently affected by deletions, no somatic copy neutral loss of heterozygosity (CN-LOH) was detected. Our data suggest that SNP-A is useful for the detection of cryptic aberrations of chromosome 20q and allows for a more precise characterization of complex karyotypes. Furthermore, SNP-A allowed definition of a CDR on 20q.