Clinicopathologic and molecular characterization of myeloid neoplasms with isolated t(6;9)(p23;q34)

Rare Hematologic Malignancies and Pre-Leukemic Entities in Children and Adolescents Young Adults

There are a variety of rare hematologic malignancies and germline predispositions syndromes that occur in children and adolescent young adults (AYAs). These entities are important to recognize, as an accurate diagnosis is essential for risk assessment, prognostication, and treatment. This descriptive review summarizes rare hematologic malignancies, myelodysplastic neoplasms, and germline predispositions syndromes that occur in children and AYAs. We discuss the unique biology, characteristic genomic aberrations, rare presentations, diagnostic challenges, novel treatments, and outcomes associated with these rare entities.

The Impact of the Chromatin Binding DEK Protein in Hematopoiesis and Acute Myeloid Leukemia

Hematopoiesis is an exquisitely regulated process of cellular differentiation to create diverse cell types of the blood. Genetic mutations, or aberrant regulation of gene transcription, can interrupt normal hematopoiesis. This can have dire pathological consequences, including acute myeloid leukemia (AML), in which generation of the myeloid lineage of differentiated cells is interrupted. In this literature review, we discuss how the chromatin remodeling DEK protein can control hematopoietic stem cell (HSC) quiescence, hematopoietic progenitor cell (HPC) proliferation, and myelopoiesis. We further discuss the oncogenic consequences of the t(6;9) chromosomal translocation, which creates the DEK-NUP214 (aka: DEK-CAN) fusion gene, during the pathogenesis of AML. Combined, the literature indicates that DEK is crucial for maintaining homeostasis of hematopoietic stem and progenitor cells, including myeloid progenitors.

t(5;12)(q31;p13)/ETV6::ACSL6 and t(6;9)(p23;q34)/DEK::NUP214 concurrence in acute myeloid leukemia: an unusual association of two rare abnormalities

The translocation t(5;12)(q31;p13)/ETV6::ACSL6 is a rare cytogenetic abnormality, although it is reported in various myeloid malignancies. To date, only 16 cases of t(5;12) and ETV6::ACSL6 rearrangement, confirmed by either molecular or Fluorescence In Situ Hyridization (FISH) analysis, have been reported. Eosinophilia is a distinctive and common feature associated with this rearrangement. Although few cases have been described, the prognosis of patients with ETV6::ACSL6 is considered poor. We report two additional cases of t(5;12)(q31;p13)/ETV6::ACLS6 rearrangement and eosinophilia. Unusually, in our cases, the ETV6::ACSL6 rearrangement occurred at the relapse of Acute Myeloid Leukemia (AML) patients who had t(6;9)(p23;q34)/DEK::NUP214 rearrangement at disease onset. The concurrence of these two rare abnormalities has never been reported and may suggest a cooperative role of t(5;12) and t(6;9), leading to disease relapse. Moreover, at relapse, both cases presented with eosinophilia, further strengthening the association of t(5;12) with eosinophilia in myeloid malignancies. Given the poor prognosis and the non-responsiveness to tyrosine kinase inhibitors of cases of ETV6::ACSL6 rearrangement, in contrast to cases of ETV6::PDGFRB rearrangement, we recommend the introduction of testing for this abnormality in myeloid malignancies with eosinophilia.

Myelodysplastic syndrome with t(6;9)(p22;q34.1)/DEK-NUP214 better classified as acute myeloid leukemia? A multicenter study of 107 cases

t(6;9)(p22;q34.1)/DEK-NUP214 is a recurrent genetic abnormality that occurs in 1-2% of patients with acute myeloid leukemia (AML), and rarely in myelodysplastic syndrome (MDS). It has been suggested by others that all myeloid neoplasms with t(6;9)/DEK-NUP214 may be considered as AML, even when blast count is <20%. In this study, we compared the clinicopathologic features of 107 patients with myeloid neoplasms harboring t(6;9)/DEK-NUP214: 33 MDS and 74 AML. Compared with patients with AML, patients with MDS were older (p = 0.10), had a lower white blood cell count (p = 0.0017), a lower blast count in the peripheral blood (p < 0.0001) and bone marrow (p < 0.0001), a higher platelet count (p = 0.022), and a lower frequency of FLT3-ITD mutation (p = 0.01). In addition, basophilia was not a common feature in the patients of this cohort. Although there was no difference in overall survival between MDS and AML patients (p = 0.18) in the entire cohort, the survival curves did show a trend toward favorable survival in MDS patients. Multivariate analyses showed that initial diagnosis of MDS vs. AML and allogeneic hematopoietic stem cell transplantation were prognostic factors for survival of patients with t(6;9)/DEK-NUP214 (p = 0.008 and p < 0.0001, respectively). Our data suggest that MDS with t(6;9)/DEK-NUP214 is prognostically not equivalent to AML with t(6;9)/DEK-NUP214. These data also show that stem cell transplantation greatly improves the survival of MDS and AML patients with myeloid neoplasms associated with t(6;9)/DEK-NUP214.

Diagnosis of rare subtypes of acute myeloid leukaemia and related neoplasms

The diagnosis of acute myeloid leukaemia and related neoplasms in adults is challenging as this requires the integration of clinical findings, morphology, immunophenotype, cytogenetics, and molecular genetic findings. Lack of familiarity with rare subtypes of acute leukaemia hinders the diagnosis. In this review, we will describe diagnostic findings of several rare acute myeloid leukaemias and related neoplasms that primarily occur in adults including information on presentation, morphology, immunophenotype, genetics, differential diagnosis, and prognosis. Leukaemias discussed include blastic plasmacytoid dendritic cell neoplasm, acute myeloid leukaemia with t(6;9) (p23;q34.1); DEK-NUP214, acute myeloid leukaemia with inv(3)(q21.3q26.2) or t(3;3)(q21.3;q26.2); GATA2, MECOM, acute myeloid leukaemia with BCR-ABL1, acute leukaemias of ambiguous lineage, acute myeloid leukaemia with mutated RUNX1, pure erythroid leukaemia, acute panmyelosis with myelofibrosis, and acute basophilic leukaemia. Case studies with morphological features of the nine subtypes of acute myeloid leukaemia and related neoplasms have been included, and additional evidence available since publication of the 2016 World Health Organization Classification has been added to each subtype.

Allogeneic hematopoietic cell transplantation improves outcome of adults with t(6;9) acute myeloid leukemia: results from an international collaborative study

Acute myeloid leukemia (AML) with t(6;9)(p22;q34) is a distinct entity accounting for 1-2% of AML cases. A substantial proportion of these patients have a concomitant FLT3-ITD. While outcomes are dismal with intensive chemotherapy, limited evidence suggests allogeneic hematopoietic cell transplantation (allo-HCT) may improve survival if performed early during first complete remission. We report on a cohort of 178 patients with t(6;9)(p22;q34) within an international, multicenter collaboration. Median age was 46 years (range: 16-76), AML was de novo in 88%, FLT3-ITD was present in 62%, and additional cytogenetic abnormalities in 21%. Complete remission was achieved in 81% (n=144), including 14 patients who received high-dose cytarabine after initial induction failure. With a median follow up of 5.43 years, estimated overall survival at five years was 38% (95%CI: 31-47%). Allo-HCT was performed in 117 (66%) patients, including 89 in first complete remission. Allo-HCT in first complete remission was associated with higher 5-year relapse-free and overall survival as compared to consolidation chemotherapy: 45% (95%CI: 35-59%) and 53% (95%CI: 42-66%) versus 7% (95%CI: 3-19%) and 23% (95%CI: 13-38%), respectively. For patients undergoing allo-HCT, there was no difference in overall survival rates at five years according to whether it was performed in first [53% (95%CI: 42-66%)], or second [58% (95%CI: 31-100%); n=10] complete remission or with active disease/relapse [54% (95%CI: 34-84%); n=18] (P=0.67). Neither FLT3-ITD nor additional chromosomal abnormalities impacted survival. In conclusion, outcomes of t(6;9)(p22;q34) AML are poor with chemotherapy, and can be substantially improved with allo-HCT.

Persistent Basophilia May Suggest an "Accelerated Phase" in the Evolution of CALR-Positive Primary Myelofibrosis Toward Acute Myeloid Leukemia

Basophils are white blood cells that play an important role in the human immune system. These cells physiologically increase in number in immune response to certain allergies, chronic inflammation, and parasitic infections. Basophils are also a significant indicator for the presence of certain malignancies such as chronic myeloproliferative neoplasms and acute myeloid leukemia. In the current manuscript we present a statistically significant correlation between persistent basophilia in primary myelofibrosis (PMF) and the risk for the subsequent development of acute myeloid leukemia. We have retrospectively identified in the files of the Department of Hematology, Ion Chiricuta Clinical Cancer Center in Cluj Napoca, Romania 623 consecutive patients diagnosed with AML over a period spanning from 2008 to 2018. We afterwards identified 32 patients with AML diagnosis following a previous diagnosis of myelofibrosis (either post-PV, post-ET, or post-PMF). All the patients were diagnosed according to the WHO criteria. We subsequently established a control group consisting of 32 patients with underlying BCR-ABL-negative MPN who did not develop AML (AML-negative group). Following this, we assessed whether the AML-negative patients from our control group also had a persistent (>3 months) absolute basophilia. When comparing both groups of patients with myelofibrosis, the group with subsequent AML development and the one without AML, the follow-up did not present statistically significant differences between the two groups. In the univariate analysis, patients who progressed to AML had more frequently basophilia, longer basophilia duration, higher pre-therapy absolute, and relative basophil count and presented more frequently calreticulin (CALR) mutations. In the current study, we emphasize the need for a closer clinical monitoring for chronic MPNs with marked basophilia, with an important potential clinical impact.