First-hit SETBP1 mutations cause a myeloproliferative disorder with bone marrow fibrosis.

ABSTRACT: SETBP1 mutations are found in various clonal myeloid disorders. However, it is unclear whether they can initiate leukemia, because SETBP1 mutations typically appear as later events during oncogenesis. To answer this question, we generated a mouse model expressing mutated SETBP1 in hematopoietic tissue: this model showed profound alterations in the differentiation program of hematopoietic progenitors and developed a myeloid neoplasm with megakaryocytic dysplasia, splenomegaly, and bone marrow fibrosis, prompting us to investigate SETBP1 mutations in a cohort of 36 triple-negative primary myelofibrosis (TN-PMF) cases. We identified 2 distinct subgroups, one carrying SETBP1 mutations and the other completely devoid of somatic variants. Clinically, a striking difference in disease aggressiveness was noted, with patients with SETBP1 mutation showing a much worse clinical course. In contrast to myelodysplastic/myeloproliferative neoplasms, in which SETBP1 mutations are mostly found as a late clonal event, single-cell clonal hierarchy reconstruction in 3 patients with TN-PMF from our cohort revealed SETBP1 to be a very early event, suggesting that the phenotype of the different SETBP1+ disorders may be shaped by the opposite hierarchy of the same clonal SETBP1 variants.

Extreme thrombocytosis with an aggressive evolution harboring a novel variant of calreticulin (CALR) in exon 3.

We describe the case of a patient with extreme thrombocytosis whose evolution was rapidly fatal. No cause of secondary thrombocytosis was found. There was no sign of myelofibrosis but the megakaryocytes were small and dysplastic. The patient presented a calreticulin (CALR) variant in exon 3 (C105S), as well as concomitant mutations of ASXL1, U2AF1, and EZH2. This variant of CALR has never been described before, and after sorting, all identified mutations were found in myeloid cells but not in lymphoid cells. Therefore, the diagnosis of a frontier case of myelodysplastic syndrome/myeloproliferative neoplasm (MDS/MPN) was made. A treatment with hydroxycarbamide was started because of a high risk of thrombosis. Upon worsening of the hematological status two new mutations appeared, SETBP1 and ETV6, and the CALR mutation was still detectable, as well as the three other mutations found in the chronic stage. Our results show that this variant could contribute to MDS/MPN pathogenesis in that patient.

Progression in Myeloid Neoplasms: Beyond the Myeloblast.

Disease progression in myelodysplastic syndromes (MDS), myelodysplastic-myeloproliferative neoplasms (MDS/MPN), and myeloproliferative neoplasms (MPN), altogether referred to as myeloid neoplasms (MN), is a major source of mortality. Apart from transformation to acute myeloid leukemia, the clinical progression of MN is mostly due to the overgrowth of pre-existing hematopoiesis by the MN without an additional transforming event. Still, MN may evolve along other recurrent yet less well-known scenarios: (1) acquisition of MPN features in MDS or (2) MDS features in MPN, (3) progressive myelofibrosis (MF), (4) acquisition of chronic myelomonocytic leukemia (CMML)-like characteristics in MPN or MDS, (5) development of myeloid sarcoma (MS), (6) lymphoblastic (LB) transformation, (7) histiocytic/dendritic outgrowths. These MN-transformation types exhibit a propensity for extramedullary sites (e.g., skin, lymph nodes, liver), highlighting the importance of lesional biopsies in diagnosis. Gain of distinct mutations/mutational patterns seems to be causative or at least accompanying several of the above-mentioned scenarios. MDS developing MPN features often acquire MPN driver mutations (usually JAK2), and MF. Conversely, MPN gaining MDS features develop, e.g., ASXL1, IDH1/2, SF3B1, and/or SRSF2 mutations. Mutations of RAS-genes are often detected in CMML-like MPN progression. MS ex MN is characterized by complex karyotypes, FLT3 and/or NPM1 mutations, and often monoblastic phenotype. MN with LB transformation is associated with secondary genetic events linked to lineage reprogramming leading to the deregulation of ETV6, IKZF1, PAX5, PU.1, and RUNX1. Finally, the acquisition of MAPK-pathway gene mutations may shape MN toward histiocytic differentiation. Awareness of all these less well-known MN-progression types is important to guide optimal individual patient management.

Clinical Characteristics and Diagnosis of Nonaccelerating MDS/MPN-U Patient with Granulocyte Dysplasia.

BACKGROUND: The goal was to improve the clinical cognition of nonaccelerating myelodysplastic/myeloproliferative neoplasms-unclassifiable (MDS/MPN-U) and avoid misdiagnosis or delayed diagnosis. METHODS: The clinical manifestations, laboratory indicators, histopathology, and therapeutic effects of a patient with nonaccelerating MDS/MPN-U were analyzed and the relevant literature was reviewed. RESULTS: Blood routine: white blood cell 98.48 x 109/L, red blood cell 3.20 x 1012/L, basophils 0.42 x 109/L, eosinophils 1.31 x 109/L, hemoglobin 112 g/L, and platelet 113 x 109/L. Blood smears showed granulocytosis and cells at various stages, polylobular granulocytes also can be seen. Bone marrow images show granulocytosis and dysplastic neutrophils, such as binuclear granulocyte, cyclic nuclear granulocyte, nuclear punch, cytoplasm vacuoles, polylobular granulocytes and so on. Bone marrow biopsy: Bone marrow proliferation tumor, combined with cell morphology and molecular biochemistry is recommended. Gene test showed Jak-2 positive, BCR/ABL and MPL negative. Chromosome examination indicated the presence of 46, XY, add (2)(p25), del (12) (p11.2p13)[16]/46, XY. CONCLUSIONS: MDS/MPN-U with granulocytosis and dysplastic neutrophils is rare, mostly in the elderly, and the diagnosis should be made except for other myeloid tumors. Currently, there is no uniform treatment guideline or expert consensus. The treatment options are limited and need to be further confirmed by more studies. MDS/ MPN-U with granulocytosis and dysplastic neutrophils has adverse prognostic factors such as advanced age, increase of bone marrow original cells and related gene mutations. Whether the adverse prognosis is related to specific gene mutations and cytogenetic variation remains to be clarified by more research data.

Clinicopathologic Features of Therapy-Related Myeloid Neoplasms in Patients with Myeloma in the Era of Novel Therapies.

The development of therapy-related myeloid neoplasms (t-MN) is a rare complication that can occur in myeloma patients treated primarily with novel therapies. To better understand t-MNs in this context, we reviewed 66 such patients and compared them with a control group of patients who developed t-MN after cytotoxic therapies for other malignancies. The study group included 50 men and 16 women, with a median age of 68 years (range, 48-86 years). Therapies included proteasome inhibitors, immunomodulatory agents, and high-dose melphalan-based autologous stem cell transplantation (HDM-ASCT) in 64 (97%), 65 (98.5%), and 64 (97%) patients, respectively; 29 (43.9%) patients were exposed to other cytotoxic drugs besides HDM. The latency interval from therapy to t-MN was 4.9 years (range, 0.6-21.9 years). Patients who received HDM-ASCT in addition to other cytotoxic therapies had a longer latency period to t-MN compared with patients who only received HDM-ASCT (6.1 vs 4.7 years, P = .009). Notably, 11 patients developed t-MN within 2 years. Therapy-related myelodysplastic syndrome was the most common type of neoplasm (n = 60), followed by therapy-related acute myeloid leukemia (n = 4) and myelodysplastic syndrome/myeloproliferative neoplasm (n = 2). The most common cytogenetic aberrations included complex karyotypes (48.5%), del7q/-7 (43.9%), and/or del5q/-5 (40.9%). The most frequent molecular alteration was TP53 mutation, in 43 (67.2%) patients and the sole mutation in 20 patients. Other mutations included DNMT3A, 26.6%; TET2, 14.1%; RUNX1, 10.9%; ASXL1, 7.8%; and U2AF1, 7.8%. Other mutations in less than 5% of cases included SRSF2, EZH2, STAG2, NRAS, SETBP, SF3B1, SF3A1, and ASXL2. After a median follow-up of 15.3 months, 18 patients were alive and 48 died. The median overall survival after the diagnosis of t-MN in the study group was 18.4 months. Although the overall features are comparable to the control group, the short interval to t-MN (<2 years) underscores the unique vulnerable status of myeloma patients.

Haploidentical donor hematopoietic cell transplantation for myelodysplastic/myeloproliferative overlap neoplasms: results from a North American collaboration.

Haploidentical donors offer a potentially readily available donor, especially for non-White patients, for hematopoietic cell transplantation (HCT). In this North American collaboration, we retrospectively analyzed outcomes of first HCT using haploidentical donor and post-transplantation cyclophosphamide (PTCy) in myelodysplastic syndrome/myeloproliferative neoplasm (MDS/MPN) overlap neoplasms (MDS/MPN). We included 120 consecutive patients who underwent HCT using a haploidentical donor for MDS/MPN across 15 centers. Median age was 62.5 years and 38% were of non-White/Caucasian ethnicity. The median follow-up was 2.4 years. Graft failure was reported in seven of 120 (6%) patients. At 3 years, nonrelapse mortality (NRM) was 25% (95% confidence interval [CI]: 17-34), relapse 27% (95% CI: 18-36), grade 3-4 acute graftversus- host disease 12% (95% CI: 6-18), chronic graft-versus-host disease requiring systemic immunosuppression 14% (95% CI: 7-20), progression-free survival (PFS) 48% (95% CI: 39-59), and overall survival (OS) 56% (95% CI: 47-67). On multivariable analysis, NRM was statistically significantly associated with advancing age at HCT (per decade increment, subdistribution hazard ratio [sdHR] =3.28; 95% CI: 1.30-8.25); relapse with the presence of mutation in EZH2/RUNX1/SETBP1 (sdHR=2.61; 95% CI: 1.06-6.44); PFS with advancing age at HCT (per decade increment, HR=1.98, 95% CI: 1.13-3.45); and OS with advancing age at HCT (per decade increment, HR=2.01; 95% CI: 1.11-3.63) and splenomegaly at HCT/prior splenectomy (HR=2.20; 95% CI: 1.04-4.65). Haploidentical donors are a viable option for HCT in MDS/MPN, especially for those disproportionately represented in the unrelated donor registry. Hence, donor mismatch should not preclude HCT for patients with MDS/MPN, an otherwise incurable malignancy. In addition to patient age, disease-related factors including splenomegaly and high-risk mutations dominate outcomes following HCT.

Myelodysplastic/myeloproliferative neoplasm with neutrophilia (atypical chronic myeloid leukemia-aCML).

A case of myelodysplastic/myeloproliferative neoplasm with neutrophilia (aCML) with SETBP1 and ASXL1 mutations.

Atypical chronic myeloid leukemia and myelodysplastic/myeloproliferative neoplasm, not otherwise specified: 2023 update on diagnosis, risk stratification, and management.

DISEASE OVERVIEW: Atypical chronic myeloid leukemia (aCML) and myelodysplastic/myeloproliferative (MDS/MPN) neoplasms, not otherwise specified (NOS), are MDS/MPN overlap neoplasms characterized by leukocytosis, in the absence of monocytosis and eosinophilia, with <20% blasts in the blood and bone marrow. DIAGNOSIS: aCML, previously known as aCML, BCR::ABL1 negative, was renamed as aCML by the ICC classification, and as MDS/MPN with neutrophilia by the 5th edition of the WHO classification. This entity is characterized by dysplastic neutrophilia with immature myeloid cells comprising ≥10% of the white blood cell count, with prominent dysgranulopoiesis. MDS/MPN-NOS consists of MDS/MPN overlap neoplasms not meeting criteria for defined categories such as chronic myelomonocytic leukemia (CMML), MDS/MPN-ring sideroblasts-thrombocytosis (MDS/MPN-RS-T), and aCML. MUTATIONS AND KARYOTYPE: Cytogenetic abnormalities are seen in 40-50% of patients in both categories. In aCML, somatic mutations commonly encountered include ASXL1, SETBP1, ETNK1, and EZH2 whereas MDS/MPN-NOS can be further stratified by mutational profiles into CMML-like, MDS/MPN-RS-T-like, aCML-like, TP35-mutated, and "others", respectively. RISK STRATIFICATION: The Mayo Clinic aCML model stratifies patients based on age >67 years, hemoglobin <10 g/dl, and the presence of TET2 mutations into low-risk (0-1 points) and high-risk (>2 points) groups, with median survivals of 18 and 7 months, respectively. MDS/MPN-NOS patients have traditionally been risk stratified using MDS risk models such as IPSS and IPSS-R. TREATMENT: Leukocytosis and anemia are managed like lower risk MPN and MDS. DNMT inhibitors have been used in both entities with suboptimal response rates. Allogeneic stem cell transplant remains the only curative strategy but is associated with high morbidity and mortality.

Recurrent bilateral adrenal infarction with myelodysplastic/myeloproliferative neoplasm-unclassifiable (MDS/MPN-U): a case report.

BACKGROUND: Bilateral adrenal infarction is rare and only a small number of cases have been reported so far. Adrenal infarction is usually caused by thrombophilia or a hypercoagulable state, such as antiphospholipid antibody syndrome, pregnancy, and coronavirus disease 2019. However, adrenal infarction with myelodysplastic/myeloproliferative neoplasm (MDS/MPN) has not been reported. CASE PRESENTATION: An 81-year-old man with a sudden severe bilateral backache presented to our hospital. Contrast-enhanced computed tomography (CT) led to the diagnosis of bilateral adrenal infarction. Previously reported causes of adrenal infarction were all excluded and a diagnosis of MDS/MPN-unclassifiable (MDS/MPN-U) was reached, which was considered to be attributed to adrenal infarction. He developed a relapse of bilateral adrenal infarction, and aspirin administration was initiated. Partial primary adrenal insufficiency was suspected as the serum adrenocorticotropic hormone level was persistently high after the second bilateral adrenal infarction. CONCLUSION: This is the first case of bilateral adrenal infarction with MDS/MPN-U encountered. MDS/MPN has the clinical characteristics of MPN. It is reasonable to assume that MDS/MPN-U may have influenced bilateral adrenal infarction development, considering the absence of thrombosis history and a current comorbid hypercoagulable disease. This is also the first case of recurrent bilateral adrenal infarction. It is important to carefully investigate the underlying cause of adrenal infarction once adrenal infarction is diagnosed, as well as to assess adrenocortical function.

Genomics of myelodysplastic/myeloproliferative neoplasm.

Myelodysplastic/ Myeloproliferative neoplasms (MDS/MPN) demonstrate overlapping pathologic and molecular features of myelodysplastic (MDS) and myeloproliferative (MPN) neoplasms. Diagnosis is difficult based on morphology alone, requiring exclusion of various non-neoplastic causes for CBC abnormalities and morphologic findings and other myeloid neoplasms. Identifying a clonal abnormality by cytogenetics or molecular studies has vastly improved our ability to diagnose MDS/MPN and has been incorporated in the different classification schemas. Currently two separate classification systems are in use- The 5th edition WHO and international consensus classification. The two competing classifications emphasize genetic work-up and are similar on many levels; however, they do introduce diagnostic dilemma when diagnosing certain entities such as chronic myelomonocytic leukemia in the presence of NPM1 mutations. The genetic profile overlaps among different subentities; however, the combination and the incidence of mutations; together with the clinical features and morphology helps in further subclassification. In this review, we discuss the advances in molecular characterization of MDS/MPN. We attempt to summarize the differences between the various classification schemes, and highlight the changes made in the diagnostic criteria.

Myeloproliferative neoplasms and clonal haematopoiesis in patients with giant cell arteritis: a case-control and exploratory study.

OBJECTIVES: GCA is a large vessel vasculitis for which triggering factors remain unknown. Clonal haematopoiesis (CH) was associated with atherosclerosis through the induction of inflammation in myeloid cells, and data suggest that CH expansion and inflammation may support each other to induce a pro-inflammatory loop. Our objective was to describe the impact of JAK2p.V617F-mutated myeloproliferative neoplasms (MPNs) on GCA and to screen MPN-free patients for CH mutations. METHODS: We performed a retrospective case-control study comparing the characteristics of 21 GCA patients with MPN and 42 age- and gender-matched GCA patients without MPN. Also, 18 GCA patients were screened for CH through next-generation sequencing (NGS). RESULTS: The most frequent associated MPN was essential thrombocythaemia (ET; n = 11). Compared with controls, GCA patients with MPN had less-frequent cephalic symptoms (71.4 vs 97.6%; P = 0.004) and higher platelet counts at baseline [485 × 109/l (interquartile range 346-586) vs 346 (296-418); P = 0.02]. There was no difference between groups for other clinical features. Overall survival was significantly shorter in patients with MPN compared with controls [hazard ratio 8.2 (95% CI 1.2, 56.6); P = 0.03]. Finally, screening for CH using NGS in 15 GCA patients without MPN revealed CH in 33%. CONCLUSION: GCA patients with MPN display higher platelet counts and shorter overall survival than controls. This association is not fortuitous, given the possible pathophysiological relationship between the two diseases. CH was found in one-third of GCA patients, which may be higher than the expected prevalence for a similar age, and should be confirmed in a larger cohort.

Molecular landscape and clonal architecture of adult myelodysplastic/myeloproliferative neoplasms.

More than 90% of patients with myelodysplastic/myeloproliferative neoplasms (MDSs/MPNs) harbor somatic mutations in myeloid-related genes, but still, current diagnostic criteria do not include molecular data. We performed genome-wide sequencing techniques to characterize the mutational landscape of a large and clinically well-characterized cohort including 367 adults with MDS/MPN subtypes, including chronic myelomonocytic leukemia (CMML; n = 119), atypical chronic myeloid leukemia (aCML; n = 71), MDS/MPN with ring sideroblasts and thrombocytosis (MDS/MPN-RS-T; n = 71), and MDS/MPN unclassifiable (MDS/MPN-U; n = 106). A total of 30 genes were recurrently mutated in ≥3% of the cohort. Distribution of recurrently mutated genes and clonal architecture differed among MDS/MPN subtypes. Statistical analysis revealed significant correlations between recurrently mutated genes, as well as genotype-phenotype associations. We identified specific gene combinations that were associated with distinct MDS/MPN subtypes and that were mutually exclusive with most of the other MDSs/MPNs (eg, TET2-SRSF2 in CMML, ASXL1-SETBP1 in aCML, and SF3B1-JAK2 in MDS/MPN-RS-T). Patients with MDS/MPN-U were the most heterogeneous and displayed different molecular profiles that mimicked the ones observed in other MDS/MPN subtypes and that had an impact on the outcome of the patients. Specific gene mutations also had an impact on the outcome of the different MDS/MPN subtypes, which may be relevant for clinical decision-making. Overall, the results of this study help to elucidate the heterogeneity found in these neoplasms, which can be of use in the clinical setting of MDS/MPN.

How I diagnose and treat chronic myelomonocytic leukemia.

Chronic myelomonocytic leukemia (CMML) is a myelodysplastic syndrome/myeloproliferative overlap neoplasm characterized by sustained peripheral blood monocytosis and an inherent risk for transformation to acute myeloid leukemia (15-30% over 3-5 years). While CMML is morphologically classified into CMML-0, 1 and 2 based on peripheral blood and bone marrow promonocyte/blast counts, a more clinically relevant classification into dysplastic and proliferative subtypes, based on the presenting white blood cell count, is helpful in prognostication and therapeutics. CMML is a neoplasm associated with aging, occurring on the background of clonal hematopoiesis, with TET2 and SRSF2 mutations being early initiating events. The subsequent acquisitions of ASXL1, RUNX1, SF3B1 and DNMT3A mutations usually give rise to dysplastic CMML, while ASXL1, JAK2V617F and RAS pathway mutations give rise to proliferative CMML. Patients with proliferative CMML have a more aggressive course with higher rates of transformation to acute myeloid leukemia. Allogeneic stem cell transplant remains the only potential cure for CMML; however, given the advanced median age at presentation (73 years) and comorbidities, it is an option for only a few affected patients (10%). While DNA methyltransferase inhibitors are approved for the management of CMML, the overall response rates are 40-50%, with true complete remission rates of <20%. These agents seem to be particularly ineffective in proliferative CMML subtypes with RAS mutations, while the TET2mutant/ASXL1wildtype genotype seems to be the best predictor for responses. These agents epigenetically restore hematopoiesis in responding patients without altering mutational allele burdens and progression remains inevitable. Rationally derived personalized/targeted therapies with disease-modifying capabilities are much needed.

The ABNL-MARRO 001 study: a phase 1-2 study of randomly allocated active myeloid target compound combinations in MDS/MPN overlap syndromes.

BACKGROUND: Myelodysplastic/myeloproliferative neoplasms (MDS/MPN) comprise several rare hematologic malignancies with shared concomitant dysplastic and proliferative clinicopathologic features of bone marrow failure and propensity of acute leukemic transformation, and have significant impact on patient quality of life. The only approved disease-modifying therapies for any of the MDS/MPN are DNA methyltransferase inhibitors (DNMTi) for patients with dysplastic CMML, and still, outcomes are generally poor, making this an important area of unmet clinical need. Due to both the rarity and the heterogeneous nature of MDS/MPN, they have been challenging to study in dedicated prospective studies. Thus, refining first-line treatment strategies has been difficult, and optimal salvage treatments following DNMTi failure have also not been rigorously studied. ABNL-MARRO (A Basket study of Novel therapy for untreated MDS/MPN and Relapsed/Refractory Overlap Syndromes) is an international cooperation that leverages the expertise of the MDS/MPN International Working Group (IWG) and provides the framework for collaborative studies to advance treatment of MDS/MPN and to explore clinical and pathologic markers of disease severity, prognosis, and treatment response. METHODS: ABNL MARRO 001 (AM-001) is an open label, randomly allocated phase 1/2 study that will test novel treatment combinations in MDS/MPNs, beginning with the novel targeted agent itacitinib, a selective JAK1 inhibitor, combined with ASTX727, a fixed dose oral combination of the DNMTi decitabine and the cytidine deaminase inhibitor cedazuridine to improve decitabine bioavailability. DISCUSSION: Beyond the primary objectives of the study to evaluate the safety and efficacy of novel treatment combinations in MDS/MPN, the study will (i) Establish the ABNL MARRO infrastructure for future prospective studies, (ii) Forge innovative scientific research that will improve our understanding of pathogenetic mechanisms of disease, and (iii) Inform the clinical application of diagnostic criteria, risk stratification and prognostication tools, as well as response assessments in this heterogeneous patient population. TRIAL REGISTRATION: This trial was registered with ClinicalTrials.gov on August 19, 2019 (Registration No. NCT04061421).

Genomic and clinical findings in myeloid neoplasms with PDGFRB rearrangement.

Platelet-derived growth factor receptor B (PDGFRB) gene rearrangements define a unique subgroup of myeloid and lymphoid neoplasms frequently associated with eosinophilia and characterized by high sensitivity to tyrosine kinase inhibition. To date, various PDGFRB/5q32 rearrangements, involving at least 40 fusion partners, have been reported. However, information on genomic and clinical features accompanying rearrangements of PDGFRB is still scarce. Here, we characterized a series of 14 cases with a myeloid neoplasm using cytogenetic, single nucleotide polymorphism array, and next-generation sequencing. We identified nine PDGFRB translocation partners, including the KAZN gene at 1p36.21 as a novel partner in a previously undescribed t(1;5)(p36;q33) chromosome change. In all cases, the PDGFRB recombination was the sole cytogenetic abnormality underlying the phenotype. Acquired somatic variants were mainly found in clinically aggressive diseases and involved epigenetic genes (TET2, DNMT3A, ASXL1), transcription factors (RUNX1 and CEBPA), and signaling modulators (HRAS). By using both cytogenetic and nested PCR monitoring to evaluate response to imatinib, we found that, in non-AML cases, a low dosage (100-200 mg) is sufficient to induce and maintain longstanding hematological, cytogenetic, and molecular remissions.

Clinical Application for Diagnosis of Myelodysplatic/Myeloproliferative Neoplasm with Ring Sideroblasts and Thrombocytosis.

BACKGROUND: Myelodysplastic/myeloproliferative neoplasm with ring sideroblasts and thrombocytosis (MDS/ MPN-RS-T) was newly introduced as a full entity in the 2016 revision of the WHO classification. In this study, we investigated the morphologic, laboratory, and clinical features of MDS/MPN-RS-T. METHODS: We reviewed the bone marrow and genetic studies of patients whose diagnoses were coded as "refractory anemia with ring sideroblasts (RARS)" or "MDS/MPN, unclassifiable" between January 2008 and April 2018. RESULTS: A total of 8 cases fulfilled the criteria for a diagnosis of MDS/MPN-RS-T. All of them had no specific symptoms. Half of the cases had less than 450 × 109/L platelet counts by an automated hematology analyzer; however, all platelet counts exceeded 450 × 109/L when performed manually. JAK2 mutation tests were performed in 7 cases, and a heterozygous mutation was detected in 1 case. SF3B1 mutations were present in 3 of the 4 cases tested. CONCLUSIONS: When RARS is suspected in patients without thrombocytopenia, manual platelet counts should be performed. For patients with suspected essential thrombocythemia, RS evaluation through careful observation of an iron-stained slide is crucial. Since the independent evaluation of RS was reflected in the revised classification, the ambiguous disease classification becomes clearer and more consistent.

[Haploidentical hematopoietic stem cell transplantation for graft failure in myelodysplastic syndrome/myeloproliferative neoplasm-unclassifiable complicated with Stenotrophomonas maltophilia bacteremia].

A 60-year-old woman with myelodysplastic syndrome/myeloproliferative neoplasm-unclassifiable underwent unrelated bone marrow transplantation from a human leukocyte antigen (HLA) 8/8 allele-matched male donor. Neutrophil engraftment was achieved on day 29. Fluorescence in situ hybridization of sex chromosomes demonstrated complete donor chimerism. The red blood cell and platelet transfusion dependence continued, and the neutrophil count decreased gradually. Despite prolonged administration of broad-spectrum antibiotics for febrile neutropenia, blood cultures on days 46 and 58 returned positive for Stenotrophomonas maltophilia (SM). Contrast-enhanced computed tomography revealed multiple nodules of septic emboli in the lungs and kidneys, suggesting a disseminated SM infection. Antibiotic therapy was conducted based on antimicrobial susceptibility testing. However, the blood cell count failed to normalize and a secondary graft failure was diagnosed. A HLA-haploidentical peripheral-blood stem-cell transplantation from the patient's son was performed on day 134 after the initial transplantation. Neutrophil engraftment was achieved on day 11. Red blood cells and platelets were also engrafted. After the resolution of the SM bacteremia, the patient was discharged on day 63. The prognosis of the SM bacteremia with neutropenia is poor. Antibiotic treatment based on antimicrobial susceptibility testing and a second transplant from an HLA-haploidentical donor likely contributed to the successful outcome in this patient.

Cancer-associated rs6983267 SNP and its accompanying long noncoding RNA CCAT2 induce myeloid malignancies via unique SNP-specific RNA mutations.

The cancer-risk-associated rs6983267 single nucleotide polymorphism (SNP) and the accompanying long noncoding RNA CCAT2 in the highly amplified 8q24.21 region have been implicated in cancer predisposition, although causality has not been established. Here, using allele-specific CCAT2 transgenic mice, we demonstrate that CCAT2 overexpression leads to spontaneous myeloid malignancies. We further identified that CCAT2 is overexpressed in bone marrow and peripheral blood of myelodysplastic/myeloproliferative neoplasms (MDS/MPN) patients. CCAT2 induces global deregulation of gene expression by down-regulating EZH2 in vitro and in vivo in an allele-specific manner. We also identified a novel non-APOBEC, non-ADAR, RNA editing at the SNP locus in MDS/MPN patients and CCAT2-transgenic mice. The RNA transcribed from the SNP locus in malignant hematopoietic cells have different allelic composition from the corresponding genomic DNA, a phenomenon rarely observed in normal cells. Our findings provide fundamental insights into the functional role of rs6983267 SNP and CCAT2 in myeloid malignancies.

MDS/MPN-Unclassifiable with t(X;17)(q28;q21) and KANSL1-MTCP1/CMC4 Fusion Gene.

Myelodysplastic/myeloproliferative neoplasm, unclassifiable (MDS/MPN-U) is a poorly characterized entity among overlap myeloid syndromes. Recent studies have shown heterogeneous mutational profiles in this group being able to subclassify them into entities closely related to the more well-established disorders under the umbrella term of the MDS/MPN group. Recurrent cytogenetic alterations are, nonetheless, rare in MDS/MPN-U. Here, for the first time, we report a case of MDS/MPN-U with a t(X;17)(q28;q21) chromosomal rearrangement leading to the KANSL1-MTCP1 fusion gene.

Chronic myeloid neoplasms harboring concomitant mutations in myeloproliferative neoplasm driver genes (JAK2/MPL/CALR) and SF3B1.

JAK2, CALR, and MPL are myeloproliferative neoplasm (MPN)-driver mutations, whereas SF3B1 is strongly associated with ring sideroblasts (RS) in myelodysplastic syndrome (MDS). Concomitant mutations of SF3B1 and MPN-driver mutations out of the context of MDS/MPN with RS and thrombocytosis (MDS/MPN-RS-T) are not well-studied. From the cases (<5% blasts) tested by NGS panels interrogating at least 42 myeloid neoplasm-related genes, we identified 18 MDS/MPN-RS-T, 42 MPN, 10 MDS, and 6 MDS/MPN-U cases with an SF3B1 and an MPN-driver mutation. Using a 10% VAF difference to define "SF3B1-dominant," "MPN-mutation dominant," and "no dominance," the majority of MDS/MPN-RS-T clustered in "SF3B1-dominant" and "no dominance" regions. Aside from parameters as thrombocytosis and ≥15% RS required for RS-T, MDS also differed in frequent neutropenia, multilineage dysplasia, and notably more cases with <10% VAF of MPN-driver mutations (60%, p = 0.0346); MPN differed in more frequent splenomegaly, myelofibrosis, and higher VAF of "MPN-driver mutations." "Gray zone" cases with features overlapping MDS/MPN-RS-T were observed in over one-thirds of non-RS-T cases. This study shows that concomitant SF3B1 and MPN-driver mutations can be observed in MDS, MPN, and MDS/MPN-U, each showing overlapping but also distinctively different clinicopathological features. Clonal hierarchy, cytogenetic abnormalities, and additional somatic mutations may in part contribute to different disease phenotypes, which may help in the classification of "gray zone" cases.