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.     

A comprehensive cytogenetic classification of 1466 Chinese patients with de novo acute lymphoblastic leukemia

Cytogenetics and molecular cytogenetics of 1466 Chinese patients with de novo acute lymphoblastic leukemia (ALL) were studied. Cytogenetic results were available in 1175 patients. Cross-correlations of 23 subclasses of cytogenetic abnormalities were described. Childhood cases had higher incidences of normal karyotype, t(1;19), +8, 12q-, +21, +22 and high hyperdiploidy with 51-65 chromosomes, and lower incidences of t(9;22) and -5/5q- than adult ones (all p<0.05). Relationships of cytogenetic subclasses with immunophenotyping subgroups of ALL were studied. Our study presents the cytogenetic characteristics of a large series of Chinese ALL patients.     

Cytogenetic findings in primary and secondary MDS.

More than 1300 MDS cases with clonal cytogenetic abnormalities, 200 of them secondary MDS, have been reported. The most common aberrations in primary MDS are del(5q) (27%), trisomy 8 (19%), monosomy 7 (15%), der(11q) (7%), -5, der(12p) and -Y (5%), del(7q) (4%), and t(1;7), der(3q), del(13q), i(17q) and del(20q) in 2% or less. The 5q- is mostly, but not always, a del(5)(q13q33); it is the cytogenetic hall-mark of the "5q- syndrome" and is frequently found as the sole abnormality. The frequency of the aberrations varies among MDS subgroups: 5q- is most frequent in RA, -5, -7, and der(12p) are more common in CMML and especially in RAEB, and +8 and der(11q) are more often found in RARS. The most common aberrations in secondary MDS are -7 (41%), del(5q) (28%), -5 (11%), der(21q) (9%), 7q-, +8 and der(12p) (8%), t(1;7) and -12 (7%), der(17p) (6%), der(3p) and der(6p) (5%), and der(3q), der(11q), -17, -18 and der(19q) (4%). The average number of abnormalities per case is 5.3, compared with 2.9 in unspecified MDS. The frequency of cytogenetically unrelated clones is 5.7% in secondary and 4.3% in primary MDS. When the literature data are broken down by type of genotoxic exposure, it turns out that -5, -7, and der(17p) are over-represented in patients who have received chemotherapy, whereas 5q- is associated with no exposure or preceding radiotherapy only. The karyotypic profile is prognostically important: patients with -7 or complex karyotypes have a higher risk of progression to acute leukemia and shorter survival.     

Toward a clinically relevant cytogenetic classification of acute myelogenous leukemia

Cytogenetic studies with Giemsa banding were performed on the bone marrow cells of 384 patients with acute myelogenous leukemia treated between 1975 and 1983. An abnormal karyotype was detected in 54% of patients, being present in 100% of metaphases (AA) in 31% and only a proportion of cells (AN) in 22%. Specific translocations or other abnormalities were noted in 22% of patients, the most common of which were t(8;21) (q22;q22) in 7%, t(15;17) (q22;q21) and inv (16) (p13q22) in 5.5%, t(9;22) (q34;q11) in 3% and abnormalities of 11q23 in 1.3%. Loss of the Y chromosome was noted in 21 patients, associated with t(8;21) in 11 patients and the sole abnormality in eight patients (45, X, -Y). Most (66%) of the other abnormalities involved addition of chromosome 8 or loss or deletion of 5 or 7 (+8, -5 or -7, 5q- or 7q- group). The remaining patients had miscellaneous abnormalities (MA). A marked assymetry was noted in the distribution of important clinical prognostic variables such as age, sex, history of an antecedent hematologic disorder and presence of Auer rods within the various cytogenetic categories. The specific translocation/abnormalities were more common in younger patients (p less than 0.01). Analysis of response, remission duration and survival demonstrated that inv 16 and t(8;21) were favorable prognostic categories; diploid, t(15;17) and 45,X,-Y had intermediate prognosis, and all other categories were unfavorable prognostic groups. The response rate and survival for diploid patients (NN) was superior to patients with abnormalities. No difference in response rate, CR duration or survival was noted between the AA and AN groups. A prognostic classification according to cytogenetic category based on clinical associations is proposed which will be tested prospectively in subsequent studies.     

Cytogenetic and molecular genetic abnormalities in agnogenic myeloid metaplasia

Agnogenic myeloid metaplasia (AMM), a clonal hematopoietic stem cell disorder also known as chronic idiopathic myelofibrosis, is characterized by a polyclonal, or reactive, stromal proliferation, resulting from the inappropriate release of megakaryocyte/monocyte-derived growth factors. Cytogenetic studies indicate that 30% of cases possess a clonal cytogenetic abnormality at diagnosis, a figure that increases to approximately 90% following leukemic transformation. Patients with specific abnormal karyotypes have a poor prognosis and may fail to respond to androgen therapy. The incidence of chromosomal abnormalities is significantly less in younger patients, a fact that may explain their more favorable prognosis. Common findings include 13q-, 20q-, trisomy 8, and abnormalities of chromosomes 1, 7, and 9. However, detailed cytogenetic analysis has not yet led to the identification of pathogenetically relevant genes and, as a result, the molecular mechanisms responsible for the clonal proliferation remain unknown. Targeted gene screening has revealed only rare oncogenic point mutations in N-RAS, p53, and c-KIT.     

Dissecting karyotypic patterns in colorectal tumors: two distinct but overlapping pathways in the adenoma-carcinoma transition

More than 500 colorectal tumors with clonal chromosomal abnormalities have been reported. Although the pattern of aberrations is nonrandom, no specific primary or secondary karyotypic abnormality has been identified. Also, the chronological order in which the aberrations appear during disease progression is not well known. One reason why our understanding of the cytogenetic evolution is unclear is the high degree of karyotypic complexity seen in these tumors. To overcome some of these difficulties we have previously used several statistical methods that allow identification and interpretation of karyotypic pathways as well as establishment of a temporal order of appearance of the imbalances. These methods were applied on 531 colorectal tumor karyotypes. By using a resampling strategy, 1p-, +7, 7q-, and +12p were identified as early events. Two major and two minor cytogenetic pathways were identified by means of principal component analysis. The two major pathways were initiated with 1p- and +7, and the minor pathways were initiated with +12p and 7q-. The +7/+12p tumors were found to be hyperdiploid, whereas those with 1p-/7q- were pseudodiploid. We also show that the adenoma-carcinoma transition in the 1p- pathway is strongly linked to karyoytypic evolution, whereas the +7 pathway is not, and that the cytogenetic pathways are separated at both early and late stages.     

Unbalanced translocation der(1;7)(q10;p10) defines a unique clinicopathological subgroup of myeloid neoplasms.

The unbalanced translocation, der(1;7)(q10;p10), is one of the characteristic cytogenetic abnormalities found in myelodysplastic syndromes (MDS) and other myeloid neoplasms. Although described frequently with very poor clinical outcome and possible relationship with monosomy 7 or 7q- (-7/7q-), this recurrent cytogenetic abnormality has not been explored fully. Here we analyzed retrospectively 77 cases with der(1;7)(q10;p10) in terms of their clinical and cytogenetic features, comparing with other 46 adult -7/7q- cases without der(1;7)(q10;p10). In contrast with other -7/7q- cases, where the abnormality tends to be found in one or more partial karyotypes, der(1;7)(q10;p10) represents the abnormality common to all the abnormal clones and usually appears as a sole chromosomal abnormality during the entire clinical courses, or if not, is accompanied only by a limited number and variety of additional abnormalities, mostly trisomy 8 and/or loss of 20q. der(1;7)(q10;p10)-positive MDS cases showed lower blast counts (P<0.0001) and higher hemoglobin concentrations (P<0.0075) at diagnosis and slower progression to acute myeloid leukemia (P=0.0043) than other -7/7q- cases. der(1;7)(q10;p10) cases showed significantly better clinical outcome than other -7/7q cases (P<0.0001). In conclusion, der(1;7)(q10;p10) defines a discrete entity among myeloid neoplasms, showing unique clinical and cytogenetic characteristics.     

Karyotypic patterns in chronic myeloproliferative disorders: report on 74 cases and review of the literature

During the 15 year period 1975-1989, 74 cases of chronic myeloproliferative disorder (CMPD) were cytogenetically analyzed in our department. Thirty patients had polycythemia vera (PV), 23 had idiopathic myelofibrosis (MFS), 15 had idiopathic thrombocythemia (IT), and six had unclassifiable CMPD (UCMPD). The overall frequency of clonal chromosome aberrations was 36% (50% in PV, 30% in MFS, 27% in IT, and 17% in UCMPD). The frequency was markedly higher (53%) in the subset of patients who had received myelosuppressive therapy and/or had developed acute leukemia prior to the initial cytogenetic analysis. The pattern of the chromosome rearrangements in our series is in agreement with the karyotypic findings in the 411 previously reported cases of CMPD. Trisomy 8 and 9 and del(20q) dominate in PV. The picture in MFS is more heterogenous with several aberrations, dup(1q), -5, del(5q), -7, del(7q), +8, +9, del(13q), del(20q), and +21, found equally frequently. No pathognomonic chromosome aberration has been detected in IT, but t(9;22) occurs more often than other changes. Thus, although a non-random cytogenetic pattern is discernible in CMPD, there is considerable overlap both with other myeloid malignancies and among the different CMPD subtypes.     

Monosomal Karyotypes among 1147 Chinese Patients with Acute Myeloid Leukemia: Prevalence,Features and Prognostic Impact

A monosomal karyotype (MK), defined as ≥2 autosomal monosomies or a single monosomy in the presenceof additional structural abnormalities, was recently identified as an independent prognostic factor conveying anextremely poor prognosis in patients with acute myeloid leukemia (AML). In the present study, after excludingpatients with t(15;17), t(8;21), inv(16) and normal karyotypes, 324 AML patients with cytogenetic abnormalitieswere the main subject of analysis. The incidences of MK were 13% in patients aged 15 to 60 years and 18% inthose between 15 and 88 years old. MK was much more prevalent among elderly patients (p < 0.001) and wassignificantly associated with the presence of -7, -5, del(5q), abn12p, abn17p, -18 or 18q-, -20 or 20q- and CK (forall p < 0.001 except for abn12p p=0.009), and +8 or +8q was less frequent in MK+ AML(p=0.007). No correlationwas noted between monosomal karyotype and FAB subtype (p > 0.05); MK remained significantly associatedwith worse overall survival among patients with complex karyotype (p= 0.032); A single autosomal monosomycontributed an additional negative effect in OS of patients with structural cytogenetic abnormalities (P=0.008).This report presents the prevalence, feature and prognostic impact of MK among a large series of Chinese AMLpatients from a single center for the first time.     

B-cell chronic lymphatic leukemia in Hodgkin's disease. A report of two patients with unusual chromosome features

The development of B-cell chronic lymphatic leukemia in two patients who had previously been treated for Hodgkin's disease is described. In both cases aneuploidy and multiple chromosome aberrations of hemopoietic cells were evident. In one patient these changes included a clonal 14q + abnormality in association with other complex rearrangements, interpreted as translocation abnormalities involving t(6;14), 5(1;15), and t(17;19). Although the chromosome abnormalities in the other patient were nonclonal, a 14q abnormality also was detected, namely t(14q+;18q-). Other chromosome abnormalities (all nonclonal) in the two patients included translocations involving chromosome 5 and deletion of 7q in one patient and trisomy of chromosome 8 in the other. Although these abnormalities have been associated with the presence or development of non-Hodgkin's lymphoma, acute nonlymphoblastic anemia, or myelodysplastic disorders, the findings in these patients suggest that the detection of clones and potential clones with these abnormalities may be only one stage in the development of secondary malignancy.     

Chromosomal aberrations of multiple myeloma in Chinese patients at diagnosis: a study by combined G-banding and multicolor spectral karyotyping

Cytogenetic investigation of multiple myeloma (MM) has been difficult by conventional methods and most of the data have been derived from western population where incidence of MM is much higher as compared to that of Asians. The current study represents the first report of chromosomal aberrations of multiple myeloma in Chinese. We investigated 25 consecutive Chinese patients with MM for chromosomal aberrations at diagnosis using G-banding and multicolor spectral karyotyping (SKY). Of the 21 patients successfully analyzed by G-banding, 11 patients revealed cytogenetic abnormalities showing complex numerical and structural aberrations, which were further characterized with SKY. An abnormal karyotype significantly associated with blastic MM was observed. Consistent with the western literature, structural rearrangements involving chromosomes 1, 6, 8, 19, numerical abnormalities of gains in chromosomes 9, 3, and 5, and losses in chromosomes 13 and 14 were observed. However, there were notably higher incidences of -22/22q- (4/11) and structural aberrations of chromosome X but a lower incidence of -X. The biological implications of these findings, if confirmed, deserve further evaluation.     

Chromosomal analysis of non-small-cell lung cancer by multicolour fluorescent in situ hybridisation

The cytogenetic abnormalities in non-small-cell lung cancer remain elusive due primarily to the difficulty in obtaining metaphase spreads from solid tumours. We have used the molecular cytogenetic techniques of multicolour fluorescent in situ hybridisation (M-FISH) and comparative genomic hybridisation (CGH) to analyse four primary non-small-cell lung cancer samples and two established cell lines (COR-L23 and COR-L105) in order to identify common chromosomal aberrations. CGH revealed regions on 5p, 3q, 8q, 11q, 2q, 12p and 12q to be commonly over-represented and regions on 9p, 3p, 6q, 17p, 22q, 8p, 10p, 10q and 19p to be commonly under-represented. M-FISH revealed numerous complex chromosomal rearrangements. Translocations between chromosomes 5 and 14, 5 and 11 and 1 and 6 were observed in three of the six samples, with a further 14 translocations being observed in two samples each. Loss of the Y chromosome and gains of chromosomes 20 and 5p were also frequent. Chromosomes 4, 5, 8, 11, 12 and 19 were most frequently involved in interchromosomal translocations. Further investigation of the recurrent aberrations will be necessary to identify the specific breakpoints involved and any role they may have in the aetiology, diagnosis and prognosis of non-small-cell lung cancer.     

Malignant hematopoietic cell lines: in vitro models for the study of myelodysplastic syndromes

The myelodysplastic syndromes (MDS) are clonal myeloid disorders characterized by bone marrow cell dysplasia and ineffective hematopoiesis leading to peripheral refractory cytopenias. The course of the disease ranges from a chronic status with progressively impaired hematopoiesis to rapid evolution to acute myeloid leukemia (AML). A panel of continuous malignant hematopoietic cell lines has been established from the whole spectrum of MDS variants and also from the different stages of the diseases, namely from the MDS phase or the overt leukemia post-MDS phase. Ten cell lines were derived from the various MDS subtypes; 17 cell lines were established from patients with leukemia (mainly AML) post-MDS. While most cell lines display myelocytic, monocytic or erythroid features, some cell lines carry lymphoid characteristics (precursor B-cell, B-cell, or T-cell), With regard to these lymphoid MDS-derived cell lines, more detailed authentication (prove of derivation from the assumed patient) and verification (prove of the malignant nature of the cell line and derivation from the assumed neoplastic cells) are required to validate the cell lines as true in vitro representatives of MDS and to exclude any cross-contamination with other cells or immortalization of normal bystander cells. On the other hand, lymphoid MDS-derived cell lines may attest to the clonal nature of MDS which may afflict progenitor cells giving rise to lymphoid or myelomonocytoid cells. Many of the MDS-derived cell lines carry cytogenetic and molecular genetic abnormalities typically associated with MDS: gain or loss of all or parts of chromosomes 5, 7, 8 and 20 (-5/5q-, -7/7q-, + 8, 20q-); alterations of oncogenes and tumor suppressor genes (IRF-1, p15, p16, p53, RAS, RB). In summary, the present panel of cell lines provides continuously growing cells and thus unlimited cell material for use as in vitro paradigms covering the whole spectrum of MDS-related hematopoetic malignancies. Properly authenticated and verified MDS-derived cell lines which should be made freely available will represent important research tools for the study of MDS biology.     

重组人核心蛋白聚糖基因增强多柔比星对白血病K562细胞抑制作用的实验研究

 目的　探讨慢性淋巴细胞白血病（CLL）的分子遗传学异常情况及其临床意义。方法　对17例初诊CLL患者进行常规细胞遗传学（CC）检测及应用着丝粒探针CSP12（12p11.1～12q11.1）和序列特异性探针D13s25（13q14.3）、ATM（11q22.3）、RB1（13q14）、p53（17p13.1）进行间期荧光原位杂交（I-FISH）检测。结果　CC检测18.75 %患者有核型异常,1例未见核分裂象;I-FISH检测70.6 %患者有分子遗传学异常,13q-异常47.1 %（RB1缺失23.5 %、D13S25缺失29.4 %）、+12异常29.4 %、p53基因缺失11.8 %、ATM缺失5.6 %、复杂基因组异常11.8 %。分子遗传学异常与性别、年龄、乳酸脱氢酶（LDH）、β2 -微球蛋白（β2-MG）及 Binet 分期无明显相关性。结论　I-FISH是检测CLL患者基因组异常的有效手段,与CC方法相比可明显提高CLL分子遗传学异常的检出率,分子遗传学异常与临床分期及其他临床指标无明显相关性,对患者预后的意义有待进一步研究。     

Abnormalities of chromosomes 1p34-36, 4p16, 4q35, 9q11-32 and +7 represent novel recurrent cytogenetic rearrangements in chronic lymphocytic leukemia

Karyotypes were studied in over 250 cases of CLL seen at our Institution and 12 cases with a previously undescribed chromosome abnormality were identified. Cytogenetic and clinicobiological features in these patients are described. Fluorescence in situ hybridization using probes for the detection of +12 and deletions of 13q14, 17p13, and 11q22-23 was performed. Hematologic and clinical data were reviewed and a review of the literature was performed. Twelve patients were found carrying the following aberrations in the stemline: abnormalities at 1p34 (n = 2), 4p16 (n = 2), 4q35 (n = 2), 9q11-32 (n = 4) and +7 (n = 2). Trisomy 12 was found in 3 cases, whereas no case carried 13q-, 11q-, 17p-. Our data showed that (i) aberrations involving 1p34 and 4p16 as isolated chromosome anomalies were preferentially associated with early stage disease; (ii) 4q35 anomalies were associated with a relatively aggressive disease, atypical morphology and with monoclonal gammopathy; (iii) rearrangements of 9q were characterized by atypical morphology and aggressive disease with splenic involvement; (iv) +7 be may associated with +12. 1p34-36; 4p16; 4q35; 9q and chromosome 7 represent novel recurrent rearranged sites in CLL, with a 0.5-3% incidence. Transformation in these patients seemingly occured through a cytogenetic route not involving the classical CLL-associated chromosome regions. These chromosome rearrangements may be associated with peculiar hematologic features.     

Prognostic relevance of cytogenetics determined by fluorescent in situ hybridization in patients having myelofibrosis with myeloid metaplasia

BACKGROUND: In chronic myelofibrosis (MF), distinct recurrent cytogenetic aberrations have been identified but their true prognostic relevance remains uncertain. In this disease, cytogenetic studies as assessed by conventional metaphase karyotyping are limited due to the inherent difficulties in obtaining adequate bone marrow aspirates and the low proliferative capacity of the clonal cells. Interphase fluorescent in situ hybridization (FISH) can partly overcome these limitations and increase the sensitivity of cytogenetic assessment in MF. METHODS: We retrospectively analyzed formalin-fixed, paraffin embedded bone marrow sections of 107 MF patients by FISH and correlated cytogenetic findings with clinical presentation and survival. RESULTS: Chromosomal aberrations were detected in 56% of patients, with 20q- (24.3%) and 13q- (16.8%) being the most frequent ones. Importantly, cytogenetic abnormalities were found in 8/17 patients displaying a normal karyotype as assessed by conventional cytogenetics. CONCLUSIONS: Cytogenetic abnormalities in patients with MF can be detected reliably using FISH. Rare abnormalities confer an adverse outcome, but the main recurrent chromosomal aberrations do not correlate with clinical features and prognosis.     

Translocations involving the short arm of chromosome 17 in chronic B-lymphoid disorders: frequent occurrence of dicentric rearrangements and possible association with adverse outcome.

Unbalanced translocations involving chromosome arm 17p, where the TP53 tumor suppressor gene localizes, are rarely described in chronic lymphocytic leukemia and small lymphocytic lymphoma (CLL/SLL), but recent use of molecular cytogenetic techniques have indicated a significant incidence of TP53 deletions, suggesting the involvement of chromosome 17p in these disorders. By conventional karyotype, we have identified unbalanced translocations involving 17p in 14 out of 123 (11%) CLL/SLL patients with clonal abnormalities. Cases were characterized by resistance to chemotherapy and a poor clinical outcome. The karyotypes presented a high incidence of complex rearrangements and 17p translocations were characterized by various partners. In 10 cases a centric fusion was assessed by fluorescent in situ hybridization (FISH) experiments using specific centromeric probes. The incidence of dicentric translocations in these series is therefore significantly higher than usually described, arising in up to 71% (10 out of 14 cases). In all cases, translocations led to a monosomy 17p and to a TP53 monoallelic deletion. The adverse clinical outcome confirms that structural abnormalities involving chromosome 17p are associated with disease progression in patients with chronic lymphoproliferative disorders.     

Cytogenetics of non-Hodgkin's lymphoma

In the non-Hodgkin's lymphoma (NHL), recurring cytogenetic abnormalities have been identified, and significant correlations among them and morphology, immunophenotyping, and parameters of clinical outcome have been recognized. The structural involvement of the 14q32 band is substantially more frequent than are other common abnormalities, which include del(6q), i(17q), +3, +7, +12, +18, and +21. Twenty-two recurring translocations have been identified. Almost three-fourths of all breakpoints in NHL occur at sites to which lineage-determining, transformation-related genes, or fragile sites have been mapped. Besides the well-known association of the t(14;18) (q32;q21) with the follicular histologies and t(8;14)(q24;q32) with small non-cleaved cell lymphoma, several other associations between recurring cytogenetic abnormalities and morphologic subtypes have been found. Similarly, several associations between cytogenetic abnormalities and the B or T immunophenotype have been delineated. Trisomy 3 or duplications of 3p predict a favorable clinical outcome; trisomy 2 or duplication 2p and abnormalities of chromosome 17 predict a poor prognosis. Common sequential changes include a (second) 14q32 break and abnormalities of chromosomes 1 and 2. Continuing work in these areas will serve to identify more clearly those regions of the genome important to transformation, differentiation, clinical aggressiveness, and progression in NHL.     

Cytogenetic aspects of adult primary myelodysplastic syndromes: clinical implications

Myelodysplastic syndrome (MDS) is a heterogeneous disease from the clinical, biological and morphological point of view. The pathogenesis of MDS is not well established and it appears to occur complex changes in the stem cell biology. Clonal chromosomal aberrations are found in 30-50% of primary MDS and no specific cytogenetic abnormality has as yet been defined. The chromosomal abnormalities are predominantly characterized by partial/total chromosomal losses or chromosomal gains. These chromosomal abnormalities include mainly -5/del(5q), -7/del(7q), del(11q), del(12p), del(20q), -Y, and +8. The role of cytogenetic analysis in the diagnosis, prognosis, taking treatment decisions and follow up of patients with MDS has been clearly defined. Despite its difficulties in obtaining for analysis high quality metaphases conventional cytogenetics continues to be the basic technique for cytogenetic evaluation of a MDS patient. Other molecular cytogenetic methods have been shown to be complementary, without replacing the information obtained with this technique. Further investigations with both conventional and molecular cytogenetics in relation to clinical features as well as other molecular methods will undoubtedly contribute to improve understanding of the underlying genetic events responsible for the development and evolution of MDS leading to more accurate classification and management of MDS patients.