Cytogenetics in the management of mature T-cell and NK-cell neoplasms: Guidelines from the Groupe Francophone de Cytogénétique Hématologique (GFCH).

Mature T-cell and natural killer (NK)-cell neoplasms (MTNKNs) are a highly heterogeneous group of lymphomas that represent 10-15 % of lymphoid neoplasms and have usually an aggressive behavior. Diagnosis can be challenging due to their overlapping clinical, histological and immunophenotypic features. Genetic data are not a routine component of the diagnostic algorithm for most MTNKNs. Indeed, unlike B-cell lymphomas, the genomic landscape of MTNKNs is not fully understood. Only few characteristic rearrangements can be easily identified with conventional cytogenetic methods and are an integral part of the diagnostic criteria, for instance the t(14;14)/inv(14) or t(X;14) abnormality harbored by 95 % of patients with T-cell prolymphocytic leukemia, or the ALK gene translocation observed in some forms of anaplastic large cell lymphoma. However, advances in molecular and cytogenetic techniques have brought new insights into MTNKN pathogenesis. Several recurrent genetic alterations have been identified, such as chromosomal losses involving tumor suppressor genes (SETD2, CDKN2A, TP53) and gains involving oncogenes (MYC), activating mutations in signaling pathways (JAK-STAT, RAS), and epigenetic dysregulation, that have improved our understanding of these pathologies. This work provides an overview of the cytogenetics knowledge in MTNKNs in the context of the new World Health Organization classification and the International Consensus Classification of hematolymphoid tumors. It describes key genetic alterations and their clinical implications. It also proposes recommendations on cytogenetic methods for MTNKN diagnosis.

The presence of a chromosomal abnormality in cytopenia without dysplasia identifies a category of high-risk clonal cytopenia of unknown significance.

Myelodysplastic syndromes (MDS) are hematological malignancies classically defined by the presence of cytopenia(s) and dysmorphic myeloid cells. It is now known that MDS can be preceded by a pre-malignant condition called clonal cytopenia of unknown significance (CCUS), which associates a clonality marker with cytopenia in the absence of criteria of dysplasia. However, to date, it is not clear whether chromosomal abnormalities should be considered in the definition of CCUS or if they carry a prognostic impact in CCUS patients. In this study, we analyzed the clinico-biological features and outcomes of 34 patients who presented with one or more cytopenias, an absence of significant dysplasia, and a presence of a chromosomal abnormality (CA). We named this entity chromosomal abnormality with cytopenia of undetermined significance (CACtUS). We show that these patients are slightly older than MDS patients and that they more frequently presented with normocytic anemia. Most CACtUS patients exhibited only one unbalanced CA. The number and type of mutations were comparable between CACtUS patients and MDS patients. Regardless of the cytogenetic abnormality, the clinicobiological characteristics, overall survival, and risk of progression to high-risk (HR) MDS were similar between CACtUS patients and low-risk MDS patients. Thus, we suggest that CACtUS patients can be considered as HR-CCUS and should receive the follow-up regimen recommended for MDS patients.

The CADM1 tumor suppressor gene is a major candidate gene in MDS with deletion of the long arm of chromosome 11.

Myelodysplastic syndromes (MDS) represent a heterogeneous group of clonal hematopoietic stem cell disorders characterized by ineffective hematopoiesis leading to peripheral cytopenias and in a substantial proportion of cases to acute myeloid leukemia. The deletion of the long arm of chromosome 11, del(11q), is a rare but recurrent clonal event in MDS. Here, we detail the largest series of 113 cases of MDS and myelodysplastic syndromes/myeloproliferative neoplasms (MDS/MPN) harboring a del(11q) analyzed at clinical, cytological, cytogenetic, and molecular levels. Female predominance, a survival prognosis similar to other MDS, a low monocyte count, and dysmegakaryopoiesis were the specific clinical and cytological features of del(11q) MDS. In most cases, del(11q) was isolated, primary and interstitial encompassing the 11q22-23 region containing ATM, KMT2A, and CBL genes. The common deleted region at 11q23.2 is centered on an intergenic region between CADM1 (also known as Tumor Suppressor in Lung Cancer 1) and NXPE2. CADM1 was expressed in all myeloid cells analyzed in contrast to NXPE2. At the functional level, the deletion of Cadm1 in murine Lineage-Sca1+Kit+ cells modifies the lymphoid-to-myeloid ratio in bone marrow, although not altering their multilineage hematopoietic reconstitution potential after syngenic transplantation. Together with the frequent simultaneous deletions of KMT2A, ATM, and CBL and mutations of ASXL1, SF3B1, and CBL, we show that CADM1 may be important in the physiopathology of the del(11q) MDS, extending its role as tumor-suppressor gene from solid tumors to hematopoietic malignancies.

Identification of novel, clonally stable, somatic mutations targeting transcription factors PAX5 and NKX2-3, the epigenetic regulator LRIF1, and BRAF in a case of atypical B-cell chronic lymphocytic leukemia harboring a t(14;18)(q32;q21).

Diagnosis of B-cell chronic lymphocytic leukemia (B-CLL) is usually straightforward, involving clinical, immunophenotypic (Matutes score), and (immuno)genetic analyses (to refine patient prognosis for treatment). CLL cases with atypical presentation (e.g., Matutes ≤ 3) are also encountered, and for these diseases, biology and prognostic impact are less clear. Here we report the genomic characterization of a case of atypical B-CLL in a 70-yr-old male patient; B-CLL cells showed a Matutes score of 3, chromosomal translocation t(14;18)(q32;q21) (BCL2/IGH), mutated IGHV, deletion 17p, and mutations in BCL2, NOTCH1 (subclonal), and TP53 (subclonal). Quite strikingly, a novel PAX5 mutation that was predicted to be loss of function was also seen. Exome sequencing identified, in addition, a potentially actionable BRAF mutation, together with novel somatic mutations affecting the homeobox transcription factor NKX2-3, known to control B-lymphocyte development and homing, and the epigenetic regulator LRIF1, which is implicated in chromatin compaction and gene silencing. Neither NKX2-3 nor LRIF1 mutations, predicted to be loss of function, have previously been reported in B-CLL. Sequencing confirmed the presence of these mutations together with BCL2, NOTCH1, and BRAF mutations, with the t(14;18)(q32;q21) translocation, in the initial diagnostic sample obtained 12 yr prior. This is suggestive of a role for these novel mutations in B-CLL initiation and stable clonal evolution, including upon treatment withdrawal. This case extends the spectrum of atypical B-CLL with t(14;18)(q32;q21) and highlights the value of more global precision genomics for patient follow-up and treatment in these patients.

Clinical and biological features of B-cell neoplasms with CDK6 translocations: an association with a subgroup of splenic marginal zone lymphomas displaying frequent CD5 expression, prolymphocytic cells, and TP53 abnormalities.

A translocation involving the cyclin-dependent kinase 6 (CDK6) gene [t(CDK6)] is a rare but recurrent abnormality in B-cell neoplasms. To further characterise this aberration, we studied 57 cases; the largest series reported to date. Fluorescence in situ hybridisation analysis confirmed the involvement of CDK6 in all cases, including t(2;7)(p11;q21) immunoglobulin kappa locus (IGK)/CDK6 (n = 51), t(7;14)(q21;q32) CDK6/immunoglobulin heavy locus (IGH) (n = 2) and the previously undescribed t(7;14)(q21;q11) CDK6/T-cell receptor alpha locus (TRA)/T-cell receptor delta locus (TRD) (n = 4). In total, 10 patients were diagnosed with chronic lymphocytic leukaemia, monoclonal B-cell lymphocytosis or small lymphocytic lymphoma, and 47 had small B-cell lymphoma (SmBL) including 36 cases of marginal zone lymphoma (MZL; 34 splenic MZLs, one nodal MZL and one bronchus-associated lymphoid tissue lymphoma). In all, 18 of the 26 cytologically reviewed cases of MZL (69%) had an atypical aspect with prolymphocytic cells. Among the 47 patients with MZL/SmBL, CD5 expression was found in 26 (55%) and the tumour protein p53 (TP53) deletion in 22 (47%). The TP53 gene was mutated in 10/30 (33%); the 7q deletion was detected in only one case, and no Notch receptor 2 (NOTCH2) mutations were found. Immunoglobulin heavy-chain variable-region (IGHV) locus sequencing revealed that none harboured an IGHV1-02*04 gene. Overall survival was 82% at 10 years and not influenced by TP53 aberration. Our present findings suggest that most t(CDK6)+ neoplasms correspond to a particular subgroup of indolent marginal zone B-cell lymphomas with distinctive features.

Ibrutinib, obinutuzumab, and venetoclax in relapsed and untreated patients with mantle cell lymphoma: a phase 1/2 trial.

Ibrutinib, obinutuzumab, and venetoclax demonstrate synergy in preclinical models of mantle cell lymphoma (MCL). OAsIs (NCT02558816), a single-arm multicenter prospective phase 1/2 trial, aimed to determine the maximum tolerated dose of venetoclax in combination with fixed doses of ibrutinib and obinutuzumab, in relapsed MCL patients. At the venetoclax MTD, extension cohorts were opened for relapsed and untreated patients. Safety and efficacy were secondary objectives. Minimal residual disease (MRD) was assessed by allele-specific oligonucleotide quantitative polymerase chain reaction. Between 14 October 2015 and 29 May 2018, 48 patients were enrolled. No dose-limiting toxicity was reported, and venetoclax at 400 mg per day was chosen for extension. Eighteen (75%) relapsed and 8 (53%) untreated patients experienced grade 3/4 adverse events. The complete response rate assessed by positron emission tomography at the end of cycle 6 was 67% in relapsed and 86.6% in untreated patients. MRD clearance for evaluable patients was seen in 71.5% of relapsed (10/14 patients) and 100% of untreated MRD-evaluable patients (n = 12) at the end of 3 cycles. The median follow-up for relapsed patients was 17 months (range, 10-35 months). The 2-year progression-free survival (PFS) was 69.5% (95% confidence interval [CI], 52.9%-91.4%) and 68.6% (95% CI, 49.5%-95.1%) for overall survival. The median follow-up was 14 months (range, 5-19) for untreated patients, the 1-year PFS was 93.3% (95% CI, 81.5%-100%). The combination of obinutuzumab, ibrutinib, and venetoclax is well tolerated and provides high response rates, including at the molecular level, in relapsed and untreated MCL patients. This trial was registered at www.clinicaltrials.gov as #NCT02558816.

Genetic characterization of B-cell prolymphocytic leukemia: a prognostic model involving MYC and TP53.

B-cell prolymphocytic leukemia (B-PLL) is a rare hematological disorder whose underlying oncogenic mechanisms are poorly understood. Our cytogenetic and molecular assessments of 34 patients with B-PLL revealed several disease-specific features and potential therapeutic targets. The karyotype was complex (≥3 abnormalities) in 73% of the patients and highly complex (≥5 abnormalities) in 45%. The most frequent chromosomal aberrations were translocations involving MYC [t(MYC)] (62%), deletion (del)17p (38%), trisomy (tri)18 (30%), del13q (29%), tri3 (24%), tri12 (24%), and del8p (23%). Twenty-six (76%) of the 34 patients exhibited an MYC aberration, resulting from mutually exclusive translocations or gains. Whole-exome sequencing revealed frequent mutations in TP53, MYD88, BCOR, MYC, SF3B1, SETD2, CHD2, CXCR4, and BCLAF1. The majority of B-PLL used the IGHV3 or IGHV4 subgroups (89%) and displayed significantly mutated IGHV genes (79%). We identified 3 distinct cytogenetic risk groups: low risk (no MYC aberration), intermediate risk (MYC aberration but no del17p), and high risk (MYC aberration and del17p) (P = .0006). In vitro drug response profiling revealed that the combination of a B-cell receptor or BCL2 inhibitor with OTX015 (a bromodomain and extra-terminal motif inhibitor targeting MYC) was associated with significantly lower viability of B-PLL cells harboring a t(MYC). We concluded that cytogenetic analysis is a useful diagnostic and prognostic tool in B-PLL. Targeting MYC may be a useful treatment option in this disease.

Poor prognosis of chromosome 7 clonal aberrations in Philadelphia-negative metaphases and relevance of potential underlying myelodysplastic features in chronic myeloid leukemia.

Clonal chromosome abnormalities in Philadelphia-negative cells could concern chronic myeloid leukemia patients treated by tyrosine kinase inhibitors. The European LeukemiaNet distinguishes -7/del(7q) abnormalities as a "warning". However, the impact of clonal chromosome abnormalities, and specifically those of -7/del(7q), in Philadelphia-negative cells on clinical outcomes is unclear and based on case-reports showing morphological dysplasia and increased risk of acute myeloid leukemia, suggesting the coexistence of chronic myeloid leukemia and high-risk myelodysplastic syndrome. The aim of this study was to determine whether the impact of -7/del(7q) clonal chromosome abnormalities in Philadelphia-negative cells on the clinical outcome is different from that of other types of abnormalities, and we argue for an underlying associated high-risk myelodysplastic syndrome. Among 102 chronic myeloid leukemia patients with clonal chromosome abnormalities in Philadelphia-negative cells with more than a median of 6 years of follow up, patients with -7/del(7q) more frequently had signs of dysplasia, a lower cumulative incidence of deep molecular response and often needed further treatment lines, with the consequent impact on event-free and progression-free survival. Morphological features of dysplasia are associated with myelodysplastic syndrome/acute myeloid leukemia mutations and compromise the optimal response to tyrosine kinase inhibitors, irrespectively of the type of clonal chromosome abnormalities in Philadelphia-negative cells. However, mutation patterns determined by next-generation sequencing could not clearly explain the underlying high-risk disease. We hereby confirm the pejorative prognostic value of -7/del(7q) clonal chromosome abnormalities in Philadelphia-negative cells and suggest that myelodysplastic features constitute a warning signal that response to tyrosine kinase inhibitors may be less than optimal.

B-ALL With t(5;14)(q31;q32); IGH-IL3 Rearrangement and Eosinophilia: A Comprehensive Analysis of a Peculiar IGH-Rearranged B-ALL.

Background: B-cell acute lymphoblastic leukemia associated with t(5;14)(q31;q32); IGH-IL3 is an exceptional cause of eosinophilia. The IGH enhancer on 14q32 is juxtaposed to the IL3 gene on 5q31, leading to interleukin-3 overproduction and release of mature eosinophils in the blood. Clinical, biological and outcome data are extremely scarce in the literature. Except for eosinophilia, no relevant common feature has been highlighted in these patients. However, it has been classified as a distinct entity in the World Health Organization classification. Cases Presentation: Eight patients with t(5;14)(q31;q32) treated by French or Austrian protocols were retrospectively enrolled. Array comparative genomic hybridization, multiplex ligation-dependent probe amplification or genomic PCR search for IKZF1 deletion were performed in 7. Sixteen patients found through an exhaustive search in the literature were also analyzed. For those 24 patients, median age at diagnosis is 14.3 years with a male predominance (male to female ratio = 5). Eosinophilia-related symptoms are common (neurologic in 26%, thromboembolic in 26% or pulmonary in 50%). Median white blood cells count is high (72 × 109/L) and linked to eosinophilia (median: 32 × 109/L). Peripheral blasts are present at a low level or absent (median: 0 × 109/L; range: 0-37 × 109/L). Bone marrow morphology is marked by a low blast infiltration (median: 42%). We found an IKZF1 deletion in 5 out of 7 analyzable patients Outcome data are available for 14 patients (median follow-up: 28 months): 8 died and 6 are alive in complete remission. Some of these features are concordant with those seen in patients with other IGH-rearranged B-cell acute lymphoblastic leukemias: young age at onset, male sex, low blast count, high incidence of IKZF1 deletion and intermediate prognosis. Conclusion: Based on shared epidemiological and biological features, B-cell acute lymphoblastic leukemia with t(5;14)(q31;q32) is a peculiar subset of IGH-rearranged B-cell acute lymphoblastic leukemia with an intermediate prognosis and particular clinical features related to eosinophilia.

Potential added value of a RT-qPCR method of SOX 11 expression, in the context of a multidisciplinary diagnostic assessment of B cell malignancies.

BACKGROUND: Expression of SRY [sex-determining region Y]-box11 (SOX11) is specific to mantle cell lymphoma (MCL) and contributes, in conjunction with immunoglobulin variable heavy chain gene mutation status, to the identification of two forms of this disease. METHODS: The aim of this report was firstly, to design an easy and suitable RT-qPCR method to quantify SOX11 mRNA expression in mantle cell lymphoma and other B cell malignancies with the proper reference gene; secondly, to define the best threshold of relative quantity of SOX11 mRNA in order to reach the best compromise between sensitivity and specificity. RESULTS: For best discrimination of MCL and non-MCL groups we determined an area under the curve (AUC) of 0.9750 and a threshold of 1.76 with 100% sensitivity and 88% specificity. AUC and threshold values of respectively 0.91/1.346 [87% sensitivity, 80% specificity] and 0.9525/1.7120 [100% sensitivity, 88% specificity] for GAPDH and RPLP0 respectively denote that the RPLP0 reference gene alone is sufficient for PCR housekeeping gene. CONCLUSION: This work describes an RT-qPCR assay for SOX11 expression in order to better characterize MCL at diagnosis. Further studies on larger cohorts are needed to evaluate this molecular tool, especially for the follow-up of minimal residual disease.

"Double-hit" chronic lymphocytic leukemia: An aggressive subgroup with 17p deletion and 8q24 gain.

Chronic lymphocytic leukemia (CLL) with 17p deletion (17p-) is associated with a lack of response to standard treatment and thus the worst possible clinical outcome. Various chromosomal abnormalities (including unbalanced translocations, deletions, ring chromosomes and isochromosomes) result in the loss of 17p and one copy of the TP53 gene. The objective of the present study was to determine whether the type of chromosomal abnormality leading to 17p- and the additional aberrations influenced the prognosis in a series of 195 patients with 17p-CLL. Loss of 17p resulted primarily from an unbalanced translocation (70%) with several chromosome partners (the most frequent being chromosome 18q), followed by deletion 17p (23%), monosomy 17 (8%), isochromosome 17q [i(17q)] (5%) and a ring chromosome 17 (2%). In a univariate analysis, monosomy 17, a highly complex karyotype (≥5 abnormalities), and 8q24 gain were associated with poor treatment-free survival, and i(17q) (P = .04), unbalanced translocations (P = .03) and 8q24 gain (P = .001) were significantly associated with poor overall survival. In a multivariate analysis, 8q24 gain remained a significant predictor of poor overall survival. We conclude that 17p deletion and 8q24 gain have a synergistic impact on outcome, and so patients with this "double-hit" CLL have a particularly poor prognosis. Systematic, targeting screening for 8q24 gain should therefore be considered in cases of 17p- CLL.

Cytogenetics in the management of lymphomas and lymphoproliferative disorders in adults and children: an update by the Groupe francophone de cytogénétique hématologique (GFCH).

Non-Hodgkin's lymphomas and lymphoproliferative disorders include a high number of heterogeneous entities, described in the 2008 WHO classification. This classification reflects the crucial role of a multidisciplinary approach which integrates cytogenetic results both for the notion of clonality and for differential diagnosis between these entities. The prognostic impact of some cytogenetic abnormalities or genome complexity is also confirmed for many of these entities. Novel provisional entities have been described, such as BCLU (B-cell lymphoma unclassifiable with features intermediate between diffuse large B-cell lymphoma and Burkitt lymphoma) for which karyotype is critical to distinguish BCLU from Burkitt's lymphoma. The karyotype can be established from any tumour or liquid infiltrated by lymphoma cells. Recent adaptations of technics for cellular cultures according to the subtype of known (or suspected) lymphoma have significantly improved the percentage of informative karyotypes. Conventional karyotypes remain the best technical approach recommended for most of these subtypes. Interphase and/or metaphase FISH also represents a solid and rapid approach, because of the significant number of recurrent (sometimes specific) rearrangements of these entities. Next generation sequencing technologies contribute to enrich genomic data and substantially improve the understanding of oncogenic mechanisms underlying these lymphoid malignancies. Some molecular biomarkers are already part of the diagnostic process (for example, somatic mutation of MYD88 in Waldenström disease) thus reinforcing the essential principle of a multidisciplinary approach for the diagnosis of all the mature lymphoid malignancies.

14q deletions are associated with trisomy 12, NOTCH1 mutations and unmutated IGHV genes in chronic lymphocytic leukemia and small lymphocytic lymphoma.

Deletions of the long arm of chromosome 14 [del(14q)] are rare but recurrently observed in mature B-cell neoplasms, particularly in chronic lymphocytic leukemia (CLL). To further characterize this aberration, we studied 81 cases with del(14q): 54 of CLL and 27 of small lymphocytic lymphoma (SLL), the largest reported series to date. Using karyotype and fluorescence in situ hybridization (FISH), the most frequent additional abnormality was trisomy 12 (tri12), observed in 28/79 (35%) cases, followed by del13q14 (12/79, 15%), delTP53 (11/80, 14%) delATM (5/79, 6%), and del6q21 (3/76, 4%). IGHV genes were unmutated in 41/53 (77%) patients, with a high frequency of IGHV1-69 (21/52, 40%). NOTCH1 gene was mutated in 14/45 (31%) patients. There was no significant difference in cytogenetic and molecular abnormalities between CLL and SLL. Investigations using FISH and SNP-array demonstrated the heterogeneous size of the 14q deletions. However, a group with the same del(14)(q24.1q32.33) was identified in 48% of cases. In this group, tri12 (P = 0.004) and NOTCH1 mutations (P = 0.02) were significantly more frequent than in the other patients. In CLL patients with del(14q), median treatment-free survival (TFS) was 27 months. In conclusion, del(14q) is associated with tri12 and with pejorative prognostic factors: unmutated IGHV genes (with over-representation of the IGHV1-69 repertoire), NOTCH1 mutations, and a short TFS.

Chromosomal translocations involving the IGH@ locus in B-cell precursor acute lymphoblastic leukemia: 29 new cases and a review of the literature.

Chromosomal translocations involving the immunoglobulin heavy chain locus (IGH@) are recurrent but rare in B-cell precursor acute lymphoblastic leukemia (BCP-ALL), and various partner genes have been described. Here, we report a new series of 29 cases of BCP-ALL with IGH@ translocations. The partner gene was identified by fluorescence in situ hybridization and/or molecular cloning in 20 patients. Members of the CEBP gene family (n = 11), BCL2 (n = 3), ID4 (n = 3), EPOR (n = 2), and TRA/D@ (n = 1) were identified and demonstrated by quantitative real-time reverse transcriptase-polymerase chain reaction to be markedly up-regulated. The present cases, added to those already reported, confirm the diversity of the partner genes, which, apart from BCL2, are specific to BCP-ALL. Collectively, patients with IGH@ translocations may represent a novel sub-group of BCP-ALL occurring in adolescents and young adults.

Patterns of genomic aberrations suggest that Burkitt lymphomas with complex karyotype are distinct from other aggressive B-cell lymphomas with MYC rearrangement.

We previously showed that complex karyotypes (CK) and chromosome 13q abnormalities have an adverse prognostic impact in childhood Burkitt lymphomas/leukemias (BL) and diffuse large B-cell lymphomas (DLBCL). The aim of our study was to identify recurrent alterations associated with MYC rearrangements in aggressive B-cell lymphomas with CK. Multicolor fluorescence in situ hybridization (M-FISH) was performed in 84 patient samples (59 adults and 25 children), including 37 BL (13 lymphomas and 24 acute leukemias), 12 DLBCL, 28 B-cell lymphomas with intermediate features (DLBCL/BL), 4 B-cell precursor acute lymphoblastic leukemias (BCP-ALL), and 3 unclassifiable B-cell lymphomas. New (cytogenetically undetected) abnormalities were identified in 80% of patients. We also refined one-third of the chromosomal aberrations detected by karyotyping. M-FISH proved to be more useful in identifying chromosomal partners involved in unbalanced translocations and in revealing greater complexity of 13q rearrangements. Most of the newly identified or refined recurrent alterations involved 1q, 13q and 3q (gains/losses), 7q and 18q (gains), or 6q (losses), suggesting that these secondary aberrations may play a role in lymphomagenesis. Several patterns of genomic aberrations were identified: 1q gains in BL, trisomies 7 in DLBCL, and 18q-translocations in adult non-BL. BCP-ALL usually displayed an 18q21 rearrangement. BL karyotypes were less complex and aneuploid than those of other MYC-rearranged lymphomas. BCP-ALL and DLBCL/BL were associated with a higher rate of early death than BL and DLBCL. These findings support the categorization of DLBCL/BL as a distinct entity and suggest that BL with CK are indeed different from other aggressive MYC-rearranged lymphomas, which usually show greater genetic complexity. © 2012 Wiley Periodicals, Inc.

Heat Shock Protein 90 is overexpressed in high-risk myelodysplastic syndromes and associated with higher expression and activation of Focal Adhesion Kinase.

Myelodysplastic syndromes are characterized by a high risk of evolution into acute myeloid leukaemia which can involve activation of signalling pathways. As the chaperone heat shock protein 90 (HSP90) has a key role in signal transduction, we investigated its role in the pathogenesis and evolution of myelodysplastic syndromes. Expressions of HSP90 and signalling proteins clients (phosphorylated-AKT (pAKT), Focal Adhesion Kinase (FAK) and phosphorylated-FAK (pFAK)), were assessed in bone marrow mononuclear and CD34-positive (CD34+) cells from 177 patients with myelodysplasia. Effects of HSP90 inhibition were also evaluated in 39 samples. The levels of all proteins studied were significantly higher in patients with high grade disease, than those with low grade myelodysplastic syndrome or chronic myelomonocytic leukaemia. High levels of HSP90, FAK, pFAK and pAKT were associated with shorter survival and increased risk of progression into acute leukaemia. A down regulation of pFAK and pAKT and increased apoptosis was observed in mononuclear and CD34+ cells after 12 hours of incubation with 17-AAG. In conclusion, our data suggest the implication of HSP90 and FAK and AKT activation in the pathogenesis of myelodysplastic syndromes with excess of blasts and evolution to leukaemia. Moreover this signalling network could be a therapeutic target through HSP90 inhibition.