ider(20q) in Myeloid Malignancies

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ider(20q) in Myeloid Malignancies

Identity

Partial karyotypes for ider(20q) in G-banding (left) and R-banding (right).

Clinics and Pathology

Disease Myelodysplastic syndrome (21 cases), Acute Myeloid Leukemia (5 cases), Chronic Myelomonocytic Leukemia (1 case).

Phenotype / cell stem origin Thrombopenia (90%) with anemia (60%).
Dysplastic changes in bone marrow: dyserythropoeisis associated with dysgranulopoieisis and/or dysmegakaryocytopoeisis.

Epidemiology The frequency of ider(20q) is estimated at 0.49% in myelodysplastic syndrome and 0.26% in acute myeloid leukemia according to one study.
They are found in older patients (average age: 68 years; range: 38-91).

Prognosis Prognosis of patients with ider(20q) seems to be poor compared to patients with del(20q), but it is unclear due to the small number of cases.

Cytogenetics

Cytogenetics Morphological A monosomy of chromosome 20 with small metacentric marker chromosome: 46,XX or XY,-20,+mar is most likely an isoderivative of chromosome 20.
The ider(20)(q10)del(20)(q11q13) is a variant of del(20)(q11q13).

Ideograms of normal chromosome 20, of del(20q), of ider(20q) and commonly deleted regions (CDR1, CDR2) and commonly retained regions (CRR1 et CRR2).
The ider(20q) is described as a secondary event, signing a clonal evolution of deletion 20q positive cells.
The formation of ider(20q) results from loss of the short arm of chromosome 20 and duplication of the deleted long arm of chromosome 20.

Cytogenetics Molecular The ider(20q) is monocentric or dicentric.
The proximal breakpoints are consistently located in 20q11.21 band. The distal breakpoints span from band 20q13.13 to band 20q13.33.
The commonly deleted region include the short arm of chromosome 20 and a large region on the long arm of chromosome 20 spanning from 20q11.21 to 20q13.13.
A commonly proximal retained region (from centromere to 20q11.21) and commonly distal retained region (from 20q13.33 to telomere 20qter) of the long arm of chromosome 20 were determined. These retained regions are duplicated.

FISH with subtelomeric probes 20p (Green signal) and 20q (Red signals). The ider(20q) contains two red signals and no green signal.

Additional anomalies Additional anomalies in decreasing frequency:
del(20q) detected by conventional cytogenetics and/or by FISH
2 copies of ider(20q)
monosomy 7
complex karyotypes in acute myeloid leukemia

Genes involved and Proteins

Note To explain specific phenotype, loss of tumor suppressor genes in deleted region ( ADA, L3MBTL ) and gene dosage effect of genes located on the retained region of chromosome 20 are suggested.

Bibliography

Clinical and molecular cytogenetic studies in seven patients with myeloid diseases characterized by i(20q-).

Li T, Xue Y, Wu Y, Pan J.

Br J Haematol 2004; 125(3):337-342.

PMID 15086414

Isochromosome of a deleted 20q may be a relatively common abnormality in myeloid malignancies.

Ligon AH, DeAngelo DJ, Atkins L, Dal Cin P.

Cancer Genet Cytogenet 2005; 162(1):89-91.

PMID 16157208

A comparison of two contrasting recurrent isochromosomes 20 found in myelodysplastic syndromes suggests that retention of proximal 20q is a significant factor in myeloid malignancies.

Mackinnon RN, Campbell LJ.

Cancer Genet Cytogenet 2005; 163(2):176-179.

PMID 16337864

Isochromosome of a deleted 20q: a rare but recurrent chromosome abnormality in myelodysplastic syndromes.

Saunders K, Czepulkowski B, Sivalingam R, Hayes JPLA, Aldouri M, Sekhar M et al.

Cancer Genet Cytogenet 2005; 156:154-157.

PMID 15642396

FISH studies identify the i(20q-) anomaly as a der(20)del(20)(q11q13)idic(20)(p11).

Li T, Xue Y, Wu Y, Pan J.

Genes Chromosomes Cancer 2006; 45(6):536-539.

PMID 16506189

Contributor(s)

Written 04-2008 Nathalie Douet-Guilbert, Jean-Luc Laï, Joris Andrieux, Audrey Basinko, Marie-Josée Le Bris, Frédéric Morel, Marc De Braekeleer

Laboratoire dÕHistologie, dÕEmbryologie et de Cytogénétique, Université de Bretagne Occidentale, Faculté de Médecine et des Sciences de la Santé, UMR-S613, Brest F-29200, France (NDG, AB, MJLB, FM, MDB); INSERM U613, Brest F-29200, France (NDG, FM, MDB); Laboratoire de Génétique Médical, Hopital Jeanne de Flandre, CHRU de Lille, France (JLL, JA)

Citation

This paper should be referenced as such :
Douet-Guilbert N, Laï JL, Andrieux J, Basinko A, Le Bris MJ, Morel F, De Braekeleer M . ider(20q) in Myeloid Malignancies. Atlas Genet Cytogenet Oncol Haematol. April 2008 .
URL : http://AtlasGeneticsOncology.org/Genes/ider20qMMID1481.html

© Atlas of Genetics and Cytogenetics in Oncology and Haematology
indexed on : Mon Aug 11 21:19:28 2008

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For comments and suggestions or contributions, please contact us

j.l.huret@chu-poitiers.fr.

Disease	Myelodysplastic syndrome (21 cases), Acute Myeloid Leukemia (5 cases), Chronic Myelomonocytic Leukemia (1 case).
Phenotype / cell stem origin	Thrombopenia (90%) with anemia (60%). Dysplastic changes in bone marrow: dyserythropoeisis associated with dysgranulopoieisis and/or dysmegakaryocytopoeisis.
Epidemiology	The frequency of ider(20q) is estimated at 0.49% in myelodysplastic syndrome and 0.26% in acute myeloid leukemia according to one study. They are found in older patients (average age: 68 years; range: 38-91).
Prognosis	Prognosis of patients with ider(20q) seems to be poor compared to patients with del(20q), but it is unclear due to the small number of cases.

Cytogenetics Morphological	A monosomy of chromosome 20 with small metacentric marker chromosome: 46,XX or XY,-20,+mar is most likely an isoderivative of chromosome 20. The ider(20)(q10)del(20)(q11q13) is a variant of del(20)(q11q13).


	Ideograms of normal chromosome 20, of del(20q), of ider(20q) and commonly deleted regions (CDR1, CDR2) and commonly retained regions (CRR1 et CRR2). The ider(20q) is described as a secondary event, signing a clonal evolution of deletion 20q positive cells. The formation of ider(20q) results from loss of the short arm of chromosome 20 and duplication of the deleted long arm of chromosome 20.

Cytogenetics Molecular	The ider(20q) is monocentric or dicentric. The proximal breakpoints are consistently located in 20q11.21 band. The distal breakpoints span from band 20q13.13 to band 20q13.33. The commonly deleted region include the short arm of chromosome 20 and a large region on the long arm of chromosome 20 spanning from 20q11.21 to 20q13.13. A commonly proximal retained region (from centromere to 20q11.21) and commonly distal retained region (from 20q13.33 to telomere 20qter) of the long arm of chromosome 20 were determined. These retained regions are duplicated.


	FISH with subtelomeric probes 20p (Green signal) and 20q (Red signals). The ider(20q) contains two red signals and no green signal.

Additional anomalies	Additional anomalies in decreasing frequency: del(20q) detected by conventional cytogenetics and/or by FISH 2 copies of ider(20q) monosomy 7 complex karyotypes in acute myeloid leukemia

Written	04-2008	Nathalie Douet-Guilbert, Jean-Luc Laï, Joris Andrieux, Audrey Basinko, Marie-Josée Le Bris, Frédéric Morel, Marc De Braekeleer
		Laboratoire dÕHistologie, dÕEmbryologie et de Cytogénétique, Université de Bretagne Occidentale, Faculté de Médecine et des Sciences de la Santé, UMR-S613, Brest F-29200, France (NDG, AB, MJLB, FM, MDB); INSERM U613, Brest F-29200, France (NDG, FM, MDB); Laboratoire de Génétique Médical, Hopital Jeanne de Flandre, CHRU de Lille, France (JLL, JA)