Introduction: Acute myeloid leukemia (AML) post myeloproliferative neoplasm (MPN) have very poor prognosis and are often excluded from most clinical trials. Methods: We retrospectively collected data from 166 patients, including 156 with available treatment data and 83 with NGS data treated in France and USA. Results: 2022 ELN risk categories were favorable, intermediate and adverse in 3 (2%), 17 (13%), and 110 (85%), respectively. Overall response rate was 57%, 20%, and 25% in patients treated by intensive chemotherapy (IC), hypomethylating agents (HMAs) and BSC (including low-intensity treatments as hydroxyurea and low-dose cytarabine), respectively. A total of 31 (22%) patients underwent allogeneic stem cell transplantation (ASCT). Median overall survival (OS) was 7.2 months without significant difference between IC and HMA (9.5 and 8.6 months, respectively). OS was significantly improved in patients allografted (6.7 vs. 1.3 months, respectively, p < 0.001). Even though 2017 and 2022 ELN risk categories were not prognostic for OS, we observed a prognostic impact on OS of Lindsley’s classifier (p = 0.014). In multivariate analysis, JAK2 mutation was associated with worse OS (p = 0.037), whereas SRSF2 showed a trend toward adverse prognosis (p = 0.057). Among functional groups, only spliceosome mutations predicted poor prognosis (p = 0.015). Conclusion: We confirmed poor prognosis of AML post-MPN. Classical prognostic classification was not validated in our cohort. We observed poor outcome using IC or HMA encouraging us to propose new clinical trials in this specific subgroup. Only ASCT was able to improve prognosis.

IntroductionElderly acute myeloid leukemia (AML) patients with poor-risk cytogenetics have a poor outcome with intensive chemotherapy (IC). While Venetoclax (VEN) has changed the outcomes of elderly unfit patients treatment, it is unknown whether it could be effective in poor-risk cytogenetics 60-75 years old patients.Materials and MethodsWe included 60-75-year-old AML patients eligible to allogenic stem cell transplantation (allo-SCT) treated with VEN (combined with azacitidine or with Cladribin and Aracytine) at Institut Paoli Calmettes, between 2020 and 2023 and compared this cohort with patients treated by IC between 2010 and 2019.ResultsTwenty six patients were treated with VEN (17 in combination with azacitidine and 9 with Cladribin and Aracytine) and 90 were treated with IC. Thirteen patients (50%) had a TP53 mutation. The median time for leucocyte and platelet counts recovery was 26 days (range 0-103) and 26 days (range, 0-63). The median duration of the first hospitalization was 32 days (ranges, 7-79). The composite response rate was 69% (CR = 50%, CRi = 4%, MLFS = 15%). Allo-SCT could be performed in 42% of cases. Median overall survival (OS) was 7.9 months (20.9 months in the group of patients who transitioned to allo-SCT). We found no difference with the historical cohort of patients treated with IC except a trend toward less lower and upper tract gastro-intestinal (GI) tract infections in the VEN group (respectively 8% vs 26%, p = .06; and 0% vs. 13% p = .06).ConclusionVEN-based treatment was found to be effective in high risk AML can be considered as an alternative to IC in patients aged 60-75 with adverse cytogenetics.

A low allele burden (i.e., <20%) of the CALR driver mutation is found in 10.8% of CALR-mutated MPNs, mostly in essential thrombocythemia, and correlates with a milder phenotype and a more indolent evolution compared to patients with an allele burden ≥20%.

OBJECTIVES:To compare the efficacy of venetoclax-azacitidine (VEN-AZA) with AZA in the real-life for patients with first relapsed or refractory acute myeloid leukaemia (R/R AML).METHODS:We retrospectively analysed R/R AML patients treated with VEN-AZA at the Institut Paoli Calmettes between September 2020 and February 2022. We compared them to a historical cohort of patients treated with AZA between 2010 and 2021.RESULTS:Thirty-five patients treated with VEN-AZA were compared with 140 patients treated with AZA. There were more favourable cytogenetics (25.7% vs. 8.6%; p = 0.01) and less FLT3-ITD mutated AML (8.8% vs. 25.5%; p = .049) in the VEN-AZA group. The overall 30-day mortality rate was 7.4% and the overall 90-day mortality was 20%, with no difference between the groups. The complete remission rate was 48.6% in the VEN-AZA group versus 15% (p < .0001). The composite complete response rate was 65.7% in the VEN-AZA group versus 23.6% (p < .0001). OS was 12.8 months in the VEN-AZA group versus 7.3 months (p = 0.059). Patients with primary refractory AML, poor-risk cytogenetics, prior hematopoietic stem-cell transplantation (HSCT) and FLT3-ITD mutated AML had lower response and survival rates.CONCLUSION:VEN-AZA was associated with a better response rate and a longer survival than AZA monotherapy in AML patients who relapsed after or were refractory to intensive chemotherapy.

Cytogenetic normal AML with NPM1 mutations forms a distinct AML entity, associated with an intermediate prognosis and a heterogeneous response to treatment. We previously described an epigenetic biomarker, defined by the level of H3K27me3 on 70kb of the HIST1 cluster in patient blast DNA. This epigenetic mark separates cytogenetically normal NPM1 mut AML into two groups of patients differing in their survival rate following chemotherapy. To better characterize the influence of the biomarker on disease progression, we performed transcriptomic and histone mark profiling on patient blasts according to the level of H3K27me3 HIST1 . Our integrated analysis revealed that the two groups of patients display differences in terms of transcriptomic, chromatin landscape and cell surface markers, which could explain the clinical difference. Our profiling revealed novel targets and therefore constitutes an (epi)transcriptomic resource for NPM1 AML. It also highlights the power of epigenetic profiling to dissect the heterogeneity of a single AML genetic entity.### Competing Interest StatementThe authors have declared no competing interest.

Introduction The last European LeukamiaNet (ELN) recommendations (Döhner H. et al. Blood. 2022) and the International Consensus Classification (ICC, Hasserjian R.P. et al. Virchows Arch. 2023) described a new entity, called myelodysplastic syndrome (MDS)/ acute myeloid leukemia (AML) with TP53 mutation ( TP53mut), comprising high-risk MDS with an excess of bone marrow blasts cells (more than 10%) and a TP53 mutation (variant allele frequency VAF ≥ 10%). They suggested that MDS and AML represent a biologic continuum rather than two distinct diseases separated by a blast cutoff. Among teams who worked on that topic, T. Grob et al. ( Blood. 2022) studied the molecular characterization of high-risk AML and MDS with TP53mut and suggested that these two types of pathologies should be considered as a single entity, with no difference in molecular characteristics or survival. In this study, we describe the clinical, cytogenetic, and molecular characteristics of a cohort of 96 MDS and AMLs with TP53mut. Patients and methods We included all the patients with AML, MDS/AML, MDS with increased blasts (MDS-IB1) and MDS-low blast (MDS-LB) with at least one TP53mut (VAF ≥ 1%) received between Aug. 2020 and Dec. 2022 at the Institut Paoli-Calmettes (IPC, Marseille, France). Clinical and biological data were extracted retrospectively from the AML IPC database. Morphologic and cytogenetic data were analyzed by standard techniques. NGS was performed using a custom targeted panel of 60 genes (Custom Myeloid Lymphoid Solution, SOPHIA GENETICS). Results We registered 96 patients with a TP53 mutation (VAF ≥ 1%), divided into AML (n=60), MDS/AML (n=14), MDS-IB1 (n=12) and MDS-LB (n=10). Median age was 71 (range, 28-88). Thirty-eight patients had been treated for a prior solid malignancy and 26 patients had a history of myeloid malignancy. TP53mut was detected at diagnosis for 85 patients and at relapse or during follow-up for 12 patients (no NGS data available at diagnosis). We detected 142 mutations in the TP53 gene, mostly missense (73%) between exon 4 and exon 11 with a median VAF of 39% (Figure 1). We found 3 hotspots mutations in positions 273, 248 and 220 with respectively 9, 9 and 8 mutations. Biallelic status (presence of ≥ 2 mutations or a mutation + a deletion) was found in 66 patients (69%). Karyotypes were available for 95 patients. The karyotype was abnormal in 88% of cases, complex in 71% and unfavorable in 80% of cases according to ELN classification or Revised International Prognostic Scoring System (R-IPSS). Complete NGS analysis revealed at least one mutation in 59 of the other genes of the panel in 67 patients (70%), the most frequent being DNMT3A (22%), TET2 (17%), ASXL1 (13%) and PPM1D (11%) (Figure 2). In our cohort of TP53mut LB-MDS (n=10), we found that 9/10 patients had co-mutations in DNMT3A (n=4) , TET2 (n=6) and PPM1D (n=2) genes, 7/10 with biallelic status and 3/10 with complex karyotype. AML and MDS/AML patients with TP53mut detected at diagnosis (n=65) were treated with intensive chemotherapy (n=13), VEN-AZA (n=26), non-intensive therapy (n=14) or best supportive care (BSC, n=12). Seventeen patients were treated with allogeneic stem-cell transplantation (ASCT). With a median follow-up (FU) of 13 months, median overall survival (OS) of the whole cohort was 7 months (ranges, 1-41). Median OS in the AML and MDS/AML group was 6 months (ranges, 1-41). Patients treated with non-intensive approach had the longest median OS (15 months) compared to patients treated with intensive chemotherapy and VEN-based approaches (8 and 6 months, respectively) and patients treated with BSC (1 month, p=0.02). Patients with MDS-IB1 and MDS-LB had 11-months median OS (ranges, 1-28). The four patients treated with upfront ASCT were still alive at the last FU date and have an estimated median OS of 18.5 months (ranges, 6-26). Conclusion Our data confirm that MDS and AML with TP53 mutation are frequently associated with complex karyotypes and have a poor prognosis. nterestingly we identified mutations in PPM1D gene, involved in TP53 pathway, in 11% of cases. Patients with AML or MDS/AML treated with non-intensive approach seem to have the longest OS (15 months). Patients with MDS-IB1 or MDS-LB treated with upfront ASCT seem to have a prolonged OS (18.5 months). Clinical, functional and mechanistic studies are required to complete these findings.

We aimed to study the prognostic impact of the mutational landscape in primary and secondary myelofibrosis. The study included 479 patients with myelofibrosis recruited from 24 French Intergroup of Myeloproliferative Neoplasms (FIM) centers. The molecular landscape was studied by high-throughput sequencing of 77 genes. A Bayesian network allowed the identification of genomic groups whose prognostic impact was studied in a multistate model considering transitions from the 3 conditions: myelofibrosis, acute leukemia, and death. Results were validated using an independent, previously published cohort (n = 276). Four genomic groups were identified: patients with TP53 mutation; patients with ≥1 mutation in EZH2, CBL, U2AF1, SRSF2, IDH1, IDH2, NRAS, or KRAS (high-risk group); patients with ASXL1-only mutation (ie, no associated mutation in TP53 or high-risk genes); and other patients. A multistate model found that both TP53 and high-risk groups were associated with leukemic transformation (hazard ratios [HRs] [95% confidence interval], 8.68 [3.32-22.73] and 3.24 [1.58-6.64], respectively) and death from myelofibrosis (HRs, 3.03 [1.66-5.56] and 1.77 [1.18-2.67], respectively). ASXL1-only mutations had no prognostic value that was confirmed in the validation cohort. However, ASXL1 mutations conferred a worse prognosis when associated with a mutation in TP53 or high-risk genes. This study provides a new definition of adverse mutations in myelofibrosis with the addition of TP53, CBL, NRAS, KRAS, and U2AF1 to previously described genes. Furthermore, our results argue that ASXL1 mutations alone cannot be considered detrimental.

In 2016 the World Health Organization (WHO) has reclassified the acute erythroid/myeloid type of acute myeloid leukemia (AML) (thereafter designated M6AML), formerly described as M6a-AML by the FrenchAmerican-British cooperative group, in either AML or myelodysplastic syndrome (MDS) depending on the number of blasts. We previously proposed a molecular classification of M6-AML in adult patients using targeted next generation sequencing (tNGS) and array comparative genomic hybridization (aCGH).We showed that the adult M6-AML share the same molecular profile as the other AML and were mainly distributed in four major classes with mutations in either NPM1, transcription factors (e.g. RUNX1), splicing factors and/or chromatin modifiers (e.g. ASXL1, SRSF2, U2AF1), or TP53. This was confirmed and refined in a recent, more comprehensive study. Based on these results and on the 2016 WHO classification we revisited the gene mutations and prognosis of our series of M6-AML. No molecular differences in the number of mutations or in the molecular classes were found between the M6-AML regardless of whether they were reclassified as AML or as myelodysplastic syndromes (AEL-MDS). Thus, in our series, the WHO 2016 had no impact on the prognosis whereas molecular stratification did. M6-AML seem to be AML in their own right: although they may have some particularities such as frequent TP53 bi-allelic alteration or rare gene fusions, globally they do not have specific molecular profiles and their prognosis is similar or close to non-M6AML and better assessed by mutations. This led us to surmise that an important part of the difference between M6-AML and non-M6-AML could be due to a different leukemic cell-of-origin. To test this hypothesis, we compared the mutations present in different compartments of the cellular hierarchy of seven M6-AML and five non-M6-AML. The 12 patients were selected according to their whole bone marrow mutational status and to the availability of live cells in our biobank. In the M6-AML group, three NPM1-mutated patients, three TP53-mutated patients and one patient mutated in U2AF1 (splicing factors and/or chromatin modifiers class) were studied. The nonM6-AML group comprised three NPM1-mutated and two TP53-mutated patients. The main clinical, biological and molecular characteristics are presented in the Online Supplementary Table S1. We used multi-parameter-fluorescence-activated cell sorting (FACS) to isolate the different cell compartments of the hematopoietic hierarchy and Sanger-sequencing to establish the molecular status of each isolated subpopulation. After obtaining the written consent of the patients according to our ethical committee regulations and biobank procedures, we did a CD34 enrichment from the 12 bone marrow samples collected at diagnosis and obtained from the IPC/CRCM biobank, which operates under authorization # AC-2007-33 granted by the French Ministry of Research. Cell separation was done by using immunomagnetic CD34 beads from Milteny Biotec. To isolate the different immature subpopulations according to the classical hierarchical model of hematopoiesis, CD34 cells were subsequently costained with a mixture of eight monoclonal antibodies and then sorted using a FACSARIAIII (BD Biosciences). In parallel, the CD34 population was costained with a mixture of seven monoclonal antibodies. Cell sorting is detailed in the Online

Acute erythroid leukaemia (AEL) is a particular form of acute myeloid leukaemia (AML). It represents about 5% of AMLs and has a poor prognosis. Two subtypes are distinguished. The most frequent is M6a, characterised by an accumulation of erythroblasts and myeloblasts in the bone marrow, while M6b, in which the bone marrow is invaded only by erythroblasts at various stages of differentiation, is extremely rare. In the last classification of the World Health Organization1 M6a-AELs have been reclassified as myelodysplastic syndromes or AMLs not otherwise specified (non-erythroid subtype), according to the percentage of blast cells and dysplastic features. Molecular characterisation has shown that AELs from adult patients have the same mutations as other AMLs, but with some variations, such as more TP53 mutations and less FLT3 alterations.2-5 The AEL phenotype may be due to specific additional mutations, a different cell-of-origin or both.6 We have proposed a molecular classification of M6a-AELs with three main classes: TP53-mutated, NPM1-mutated and secondary-like.2 We describe recurrent copy number alterations (CNAs) of genes involved in erythropoiesis that are found in TP53-mutated AELs. We recently came across our first case of M6b-AEL. Molecular characterisation of this M6b-AEL (HD-2771) was performed using array-comparative genomic hybridisation (aCGH) and whole-exome sequencing (WES), as previously published.3,7 We studied DNA from whole bone marrow, CD235 + cells and CD3 + cells, obtained by cell sorting, as described previously.6 Whole-genome characterisation by aCGH (Fig 1A) showed several abnormalities in number and structure, including chromothripsis at the long arm of chromosome 10, loss of the IKZF1 gene at 7p12, amplification of part of the short arm of chromosome 19 (Fig 1B) and an additional chromosome 21. These abnormalities were seen in both the whole bone marrow and CD235 + cells but not, as expected, in the CD3 + cells. The 19p13 amplification contained, among other genes, a major determinant of erythropoiesis: the erythropoietin receptor (EPOR) gene (Fig 1C). Heterozygous losses of LYL1 and KLF1 and loss of TCF3/E2A, all coding for transcription factors involved in erythropoiesis,8 were centromeric and telomeric to the 19p amplicon respectively.WES of CD235 + cells DNA identified a missense mutation (F113V) in the TP53 gene. The variant allele frequency was 92.5%, suggesting a homozygous state. It was 2.2% in the CD3 + sample, probably the result of contamination by CD235 + cells. TP53 is frequently mutated in a homozygous state in AELs5,9,10 and, independently of its effect on the genome, may play a direct role in early erythropoiesis.11 Other noticeable variants were in genes coding for cohesin interactor PDS5B and GATA1 interactor HDAC512 (Table SI). To determine whether these CNAs could be specific to M6b or could also be found in M6a-AELs, we looked at three sets of data. First, we retrospectively searched our series of 66 characterised M6a-AELs,3 (unpublished data) for the same alterations. We found one TP53-mutated M6a case (HD-2702) with CNA of EPOR and of the ERG gene at 21q22.3 (Fig S1). Three other cases showed a loss of IKZF1/Ikaros at 7p12 (Fig S2A). Chromothripsis at chromosome arm 10q was not observed, but CNA of the region could implicate the LDB1 gene (Fig S2B). Chromothripsis has been described in AEL 5 and is likely to be the result of TP53 defects. Second, we looked at a recently published set of data.5 In this large series of adult AELs, alterations of chromosome arm 19p were frequent in TP53-mutated cases and a minimal region of loss targeted the KLF1 gene (Fig 2). Another region of loss containing TCF3 was telomeric to the EPOR CNA. Third, we looked at data on erythroleukaemia cell lines. We found that four known TP53-mutated erythroleukaemia cell lines,13 F-36P, HEL, OCI-M2 and TF-1, showed a 19p13 abnormality with EPOR CNA (Fig 2). TF-1 is known to have a rearranged EPOR gene.5,14 All four cell lines also showed ERG gain (Fig S3). We have identified here potential driver CNAs in AEL through analysis of a new case and the retrospective analysis of available data, opening perspectives for understanding and fighting the leukaemogenic mechanisms of AEL. A survey of The Cancer Genome Atlas data on AMLs did not reveal such CNAs. Although there might be other important genes in the gained and lost regions, the involvement of EPOR, ERG, TCF3, IKZF1, and perhaps KLF1, LYL1, NFIX and CALR, is both specific to and recurrent in TP53-mutated M6-AEL (whether a or b). Tempering with region 19p13 allows the cell to target several linked genes through the same event/mechanism. The amplification of the EPOR gene suggests that EPOR overexpression may be a major driver of an erythropoiesis rendered abnormal by the TP53 co-occurring mutation. It also suggests that targeting the EPOR/JAK/STAT pathway may help treat AEL. In a recent study of 12 TP53-mutated AELs, ERG overexpression was observed in two cases and was shown to sustain proliferation of mouse erythroid cells and to cooperate with TP53 mutation to transform erythroid progenitors in vitro (Fagnan et al. submitted).This result suggests that ERG plays a direct role in leukaemogenesis. Unravelling the respective role of EPOR and of the transcription factors involved will be necessary. Thus, AEL may result from mutations in common cancer genes and in specific red blood cell genes. The latter may be used as therapeutic targets, but their alterations may be less easy to detect in M6a than in M6b because of a lesser expansion, due itself to a different cell-of-origin or to a lower mutational rate. Also, what cooperation sustains leukaemogenesis in the non TP53-mutated AELs remains to be identified. Our work was supported by Inserm and Institut Paoli-Calmettes. All authors read and approved the final manuscript. JA and NC did the genome analyses and AG the bioinformatics. AM, MJM, MC and NV provided information on clinical, hematological and genomic data. DB and VGB designed the study and wrote the paper. The authors report no potential competing conflicts of interest. Table SI. Results of whole-exome sequencing of CD235+ cells from M6b-AEL HD-2771. Fig S1. aCGH analysis of M6a-AEL HD-2702 and M6b-AEL HD-2771 cases. Fig S2. (A) aCGH profile of chromosome 7 showing loss at 7p12-p14 (left panel) in M6b HD-2771, and in three M6a cases. (B) aCGH profile of chromosome 10 showing the region affected by chromothripsis on the long arm in M6b HD-2771 and a gain of the same region in M6a HD-2702. Fig S3. Study of erythroleukemia cell lines HEL and TF-1 showing abnormal aCGH profiles of chromosomes 19 and 21. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Myeloproliferative neoplasms (MPNs) are clonal disorders characterized by myeloproliferation and predisposition to bone marrow fibrosis. Philadelphia-negative classical MPNs comprise essential thro...

In myeloproliferative neoplasms (MPN), JAK2V617F allele burden measurement has an impact on prognosis that helps in patient monitoring. Less is known about its usefulness in CALR-mutated cases. Additional mutations found by next-generation sequencing have also shown an impact on prognosis that may drive therapeutic choices, especially in myelofibrosis, but few studies focused on CALR-mutated patients. We performed a molecular evaluation combining next-generation sequencing with a myeloid panel and CALR allele burden measurement at diagnosis and during follow-up in a cohort of 45 patients with CALR-mutated essential thrombocythaemia. The bone marrow histology was also blindly reviewed in order to apply the WHO2016 classification. The most frequently mutated gene was TET2 (11/21 mutations). CALR type 1-like patients appear to have a more complex molecular landscape. We found an association between disease progression and CALR allele burden increase during follow-up, independently of additional mutations and WHO2016-reviewed diagnosis. Patients with disease progression at the time of follow-up showed a significant increase in CALR allele burden (+16·7%, P = 0·005) whereas patients without disease progression had a stable allele burden (+3·7%, P = 0·194). This result argues for clinical interest in CALR allele burden monitoring.

In BCR‐ABL1‐negative myeloproliferative neoplasms, myelofibrosis (MF) is either primary (PMF) or secondary (SMF) to polycythemia vera or essential thrombocythemia. MF is characterized by an increased risk of transformation to acute myeloid leukemia (AML) and a shortened life expectancy.

AimsThis study sought to clarify the molecular pathways underlying the putative evolution from lymphomatoid papulosis (LyP) to cutaneous anaplastic large‐cell lymphoma (c‐ALCL) and lymph node invasion (LNI).Methods and resultsWe analysed nine sequential tumours from the same patient presenting with parallel evolution of LyP (n = 3) and c‐ALCL (n = 1) with LNI (n = 1), combined with systemic diffuse large B‐cell lymphoma (DLBCL) (n = 4). Clonality analysis showed a common clonal T‐cell origin in the five CD30+ lesions, and a common clonal B‐cell origin in the four DLBCL relapses. Array‐comparative genomic hybridisation and targeted next‐generation sequencing analysis demonstrated relative genomic stability of LyP lesions as compared with clonally related anaplastic large‐cell lymphoma (ALCL) tumours, which showed 4q and 22q13 deletions involving the PRDM8 and TIMP3 tumour suppressor genes, respectively. The three analysed CD30+ lesions showed mostly private (specific to each sample) genetic alterations, suggesting early divergence from a common precursor. In contrast, DLBCL tumours showed progressive accumulation of private alterations, indicating late divergence.ConclusionsSequential cutaneous and nodal CD30+ tumours were clonally related. This suggests that LyP, c‐ALCL and LNI represent a continuous spectrum of clonal evolution emerging from a common precursor of cutaneous CD30+ lymphoproliferations. Therefore, nodal ALCL tumours in the context of LyP should be considered as a form of transformation rather than composite lymphoma.

Abstract BACKGROUND Post myeloproliferative neoplasms (MPN) acute myeloid leukemia (AML) occurs respectively in 1.5%, 7.0% and 11% of patients with essential thrombocytosis (ET), polycythemia vera (PV) and primary myelofibrosis (PMF). This subgroup of AML has very poor prognosis and are often excluded from clinical trials. Therefore, only few cohorts including molecular data are available. MATERIAL AND METHODS We retrospectively collected data from 111 patients treated in four centers in France for post MPN-AML. Clinical, molecular and treatment information was available for all patients at AML and MPN stages. DNA was extracted from samples at diagnosis of MPN chronic phase, at diagnosis of AML phase and after induction treatment. JAK2-V617F mutations were identified by qPCR (Ipsogen® MutaQuant kit, Qiagen, Germany), MPL-W515L/K mutations were identified by PCR (Ipsogen® MutaScreen kit, Qiagen, Germany) and CALR mutations were identified by conventional sequencing (Applied Biosystems, 3500Genetic Analyzer). NGS on 36 genes using Ampliseq librairy and Ion Proton sequencing (Thermofisher, Waltham, MA, USA) were performed in 96/111 patients. Overall response rate (ORR) was defined by complete remission (CR), CR with incomplete hematologic recovery (CRi), partial remission (PR) and stable disease (SD). Overall survival (OS) was calculated from the date of AML diagnosis to the date of death or last follow-up. All statistical analyses were performed using SPSS v.22 software (IBM SPSS Statistics). RESULTS 111 patients treated for post MPN-AML were retrospectively included in this study. Sex ratio M/F was 54%/46%. Median age at AML diagnosis was 66 years (28-89, range). Cytogenetic categories were favorable, intermediate and adverse in 2 (2%), 51 (46%) and 47 (42%) patients, respectively. 25/111 (23%) patients had a monosomal karyotype (MK). Median number of additional mutations excluding from JAK2/MPL/CALR mutations was 2 (0-6, range). The most frequent additional mutations were TP53 (23%), ASXL1 (17%), TET2 (13%), SRSF2 (10%), DNMT3A (8%), SF3B1 (8%) and RUNX1 (8%). Only 2 patients were mutated for NPM1 and 2 and 4 patients were FLT3-ITD and FLT3-TKD, respectively. Prior MPN were PV, ET and PMF in 20%, 34% and 46% of patients, respectively. First line treatment was intensive chemotherapy (IC) for 61 (55%) patients, hypomethylating agents (HMA) for 10 (9%) or other treatments including best supportive care, cytoreduction for the other ones. 24/111 (22%) underwent to ASCT. ORR was 54% (with 30/71 (42%) in CR/CRi) in patients treated by IC or HMA. We did not identify factors predicting a higher rate of CR/CRi. OS was 12 months [6-18] and was not influenced by transplant, cytogenetic categories or by the type and allele frequencies of JAK2/CALR/MPL mutations. OS was significantly longer in the group treated with HMA as compared to IC (10 versus 46 months, respectively, p=0.006); in patients with prior PV as compared to ET or MF (26 months [0-57] versus 10 months [7-13] versus 10 months [4-16] respectively, p=0.07) and in patients with presence of additional mutations other than JAK2/CALR/MPL (5 months [0-12] versus 46 months [32-60] in 38 patients without mutation versus 58 patients with presence of at least one mutation, respectively, p=0.04). By multivariate analysis, only presence of additional mutations was predictive for OS with a hazard ratio (HR) = 0.42 [0.18-0.97] (p=0.04). Finally, we followed the VAFs of JAK2 in seven patients before and after IC. We observed in 2 patients an increase of JAK2 clone correlated with CR whereas no variation of VAFs was associated with absence of CR. CONCLUSIONS In conclusion, we confirmed the poor prognosis of post MPN AML. Classical AML prognostic factors were not validated in our cohort. We identified the presence of mutations other than JAK2/MPL/CALR as the main prognostic factor whereas post-PV AML appeared to do better than post-ET and post-PMF AML. The very poor result of IC with or without ASCT highlights the need to develop specific clinical trials in this subgroup of AML. Disclosures Kuykendall: Celgene: Honoraria; Janssen: Consultancy. Sallman:Celgene: Research Funding, Speakers Bureau. Cluzeau:CELGENE: Consultancy; MENARINI: Consultancy; JAZZ PHARMA: Consultancy.

Due to the lack of specific clinical and biological features, M6a-acute erythroid leukemia (M6a-AEL), defined as an erythroid/myeloid type of acute leukemia, is no longer a distinct entity in the last classification of myeloid neoplasms by the World Health Organization (WHO).1 The diagnosis of M6a-AEL was previously made if a proliferation of erythroid precursors 50% with a myeloblast count 20% when counted as a percentage of non-erythroid cells, was found in the bone marrow.2 In 2016, revision of the WHO classification, the denominator used for calculating the blasts percentage was changed from non-erythroid cells to all nucleated cells. Consequently, M6a-AELs are now either myelodysplastic syndromes (MDSs) if the percentage of myeloblasts is 20% of non-erythroid cells but <20% of all nucleated cells or acute myeloid leukemia (AML) if the percentage of myeloblasts is 20% of all nucleated cells. As for any other AMLs prior therapy, recurring WHO cytogenetic abnormalities, and criteria for AML with myelodysplasia-related changes (AML-MRC) have to be taken into consideration for classification.

L'érythroblastopénie est un syndrome parathymique classique. À l'inverse, la lymphocytose T polyclonale est très rare. Nous présentons le cas d'un patient porteur d'une forte lymphocytose T polyclonale au décours du traitement d'un thymome malin. Lorsque l'imagerie a confirmé la rechute, une érythroblastopénie est également apparue. Un patient de 44 ans aux antécédents de thymome de stade IV A diagnostiqué et traité en 2008 était hospitalisé en décembre 2016 pour l'exploration d'une anémie associée à une lymphocytose. Ce thymome avait été diagnostiqué sur l'analyse histologique d'une lésion pleurale droite en 2008 et était considéré en rémission après traitement par chimiothérapie de type CAP (6 cures) et une radiothérapie complémentaire sur le volume médiastinal. Malgré cette rémission apparente s'est développée sur plusieurs année une lymphocytose T polyclonale oscillant entre 20 000 et 30 000/mm3. Le patient n'avait jamais présenté de myasthénie. Il était en bon état général malgré une perte de 4 kg en 1 an, parallèlement à l'apparition d'un vitiligo. Il présentait également des douleurs thoraciques droites réapparues depuis 6 mois. Le bilan biologique montrait une hyperleucocytose à 43,5 giga/L comprenant 34,8 giga/L de lymphocytes et une anémie à 4 g/L. Le myélogramme réalisé retrouvait l'importante lymphocytose faite de petits lymphocytes matures à noyaux réguliers et mettait en évidence une érythroblastopénie. Il n'y avait pas blastes. Le phénotypage lymphocytaire sur sang circulant retrouvait une lymphocytose sanguine comportant 99 % de lymphocytes T dont 75 % étaient CD3+CD4+ et 1 % de NK. La recherche de clonalité T circulante par étude du répertoire VBeta des lymphocytes T CD4+ en cytométrie en flux ne retrouvait pas de monoclonalité. L'IRM thoracique et le TEP scanner étaient en faveur d'une récidive du thymome devant une infiltration tissulaire à point de départ pulmonaire droit envahissant l'hémichamp pulmonaire droit, le médiastin, la coupole diaphragmatique droite et la quasi-totalité du foie droit. La lymphocytose T périphérique est rarement associée aux thymomes malins. Les autres cas retrouvés dans la littérature (10 cas) sont majoritairement en rapport avec des thymomes agressifs avec invasion locale comme chez notre patient. Devant la mise en évidence d'une telle lymphocytose, il faut savoir éliminer une monoclonalité qui s'intégrerait dans une leucémie ou d'un lymphome T. Le mécanisme de la lymphocytose T polyclonale pourrait résulter des altérations de l'immunorégulation thymique accompagnant certaines néoplasies thymiques. Cette forte lymphocytose a précédé de plusieurs années la rechute évidente. De plus, à notre connaissance, c'est le seul cas où la lymphocytose s'est associée à une érythroblastopénie. Dans le contexte d'un thymome apparemment en rémission, une lymphocytose T polyclonale doit rendre extrêmement vigilant et témoigne d'une maladie toujours présente.