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+12 or trisomy 12

Written2000-05Lucienne Michaux
Department of Hematology and Center for Human Genetics Cliniques Universitaires Saint Luc Avenue Hippocrate 10 1200 Brussels, Belgium

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Note trisomy 12 is the most common cytogenetic change in chronic lymphocytic leukemia (CLL); however, it has also been observed in other subtypes of B-cell lymphoproliferative disorders, where it is not seldomly a secondary change
  Trisomy 12 Top: trisomy 12 R-banding and FISH - Courtesy Hossein Mossafa. Bottom: Detection of trisomy 12 using fluorescence in situ hybridization with the Vysis SpectrumGreen-labeled probe specific for the alpha satellite (centromeric) region, 12p11.1-q11 and with LSI D13S319 SpectrumOrange/CEP 12 SpectrumGreen probes (Abbott Molecular, US) showing 3 copies of chromosomes 12 (green signals) - Courtesy Adriana Zamecnikova.

Clinics and Pathology

Disease B-cell chronic lymphocytic leukemia (B-CLL)
Phenotype / cell stem origin virgin CD5+ recirculating B-cell; the classical CLL phenotype is CD5+, CD23+, CD22-, CD79a-, FMC7-, sIg weak; trisomy 12 is more often observed in CLL with morphologically and immunologically atypical cells, displaying CD5 negativity or FMC7 positivity and strong surface immunoglobulin staining; trisomy 12 is present in proliferating cells and seems to be associated with the absence of mutation of the Ig variable region genes
Epidemiology trisomy 12 is found in one third of cytogenetically abnormal CLLs by conventional karyotype, and in about 12-54% of cases when interphase FISH is used
Prognosis a significant difference comparing the therapy-free interval of patients with +12 and patients with other anomalies was found; this observation was repeatedly confirmed; however an adverse impact of +12 on survival could not be demonstrated until the IWCLL compiled karyotype and survival data from more than 400 patients and showed a median survival of 5.4 years versus 8.6 years versus 14 years in patients with +12 versus another single abnormality versus a normal karyotype, respectively; the preliminary results on a large series of patients analyzed by interphase FISH showed that +12 and 14q+ changes are associated with shorter survival times, compared to patients with 13q abnormalities and normal karyotypes; however prospective data are needed to further assess the prognostic value of this cytogenetic change

Disease B-cell non Hogkin's lymphomas, distinct from CLL, i.e.prolymphocytic leukemia, hairy cell leukemia, splenic lymphoma with villous lymphocytes (SLVL), Waldenström's disease, follicular lymphoma, mantle cell lymphoma, and diffuse large cell lymphoma
Phenotype / cell stem origin lack of specificity for a particular immunophenotype
Prognosis no data are available concerning the prognostic significance of +12, except in one series of mantle cell lymphomas in which it was the only single cytogenetic parameter associated with poor prognosis


Cytogenetics Morphological using restriction fragment length polymorphism analysis, the extra chromosome 12 has been shown to derive from duplication of one chromosome 12, with retention of the other homolog rather than from triplication of one homolog; trisomy 12 is thought to be a secondary change since combined immunological and cytogenetic studies showed that it is present in only a part of the neoplastic B-cells; cases with partial duplication 12q were analyzed by FISH, and a "minimal duplicated region" could be defined in segment 12q13-12q15


Trisomy 12 is uncommon in typical chronic lymphocytic leukaemias.
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FISH identifies different types of duplications with 12q13-15 as the commonly involved segment in B-cell lymphoproliferative malignancies characterized by partial trisomy 12.
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Unmutated Ig V(H) genes are associated with a more aggressive form of chronic lymphocytic leukemia.
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Cytogenetic analysis of B cell chronic lymphoid leukemias classified according to morphologic and immunophenotypic (FAB) criteria.
Hernandez JM, Mecucci C, Criel A, Meeus P, Michaux I, Van Hoof A, Verhoef G, Louwagie A, Scheiff JM, Michaux JL
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Trisomy 12 defines a group of CLL with atypical morphology: correlation between cytogenetic, clinical and laboratory features in 544 patients.
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Trisomy 12 in chronic lymphocytic leukemia detected by fluorescence in situ hybridization: analysis by stage, immunophenotype, and morphology.
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This paper should be referenced as such :
Michaux, L
+12 or trisomy 12
Atlas Genet Cytogenet Oncol Haematol. 2000;4(2):81-82.
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Other genes implicated (Data extracted from papers in the Atlas) [ 1 ]

Genes CD38

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