Acute myeloid leukaemia of mixed megakaryocytic and erythroid origin: a case report and review of the literature

Acute erythroid leukemia is enriched in NUP98 fusions: a report from the Children's Oncology Group

Acute erythroid leukemia (AEL) is a rare subtype of acute myeloid leukemia (AML) primarily affecting older adults and was previously classified into erythroid/myeloid and pure erythroid subtypes. In this pediatric AEL study, we evaluated morphologic, immunophenotypic, cytogenetic, molecular, and clinical data of 24 (1.2%) cases from all cases undergoing central pathology review in Children's Oncology Group trials AAML0531 and AAML1031. Of 24 cases, 5 had a pure erythroid phenotype, and 19 had an erythroid/myeloid phenotype. NUP98 fusions were highly enriched in patients with AEL, occurring in 7 of 22 cases for which molecular data were available (31.8% vs 6.7% in other AML subtypes). Of 5 cases of pure erythroid leukemias (PELs), 3 had NUP98 fusions, and 4 had complex karyotypes. Erythroid/myeloid leukemias were reclassified by using the 2017 World Health Organization hematopathology classification as: myelodysplastic syndrome (MDS) with excess blasts-1 (n = 3), MDS with excess blasts-2 (n = 7), AML (nonerythroid, n = 5), and unknown MDS/AML (n = 4); the 5 cases of nonerythroid AML included 1 with an NUP98-NSD1 fusion, 2 with myelodysplasia-related changes, and 1 with a complex karyotype. Three cases of MDS with excess blasts-2 also had NUP98 rearrangements. WT1 mutations were present in 5 of 14 cases, all erythroid/myeloid leukemia. Outcomes assessment revealed statistically poorer overall survival (5-year, 20% ± 36% vs 66% ± 23%; P = .004) and event-free survival (5-year, 20% ± 36% vs 46% ± 23%; P = .019) for those with PEL than those with erythroid/myeloid leukemia. Our study supports that AEL is a morphologically and genetically heterogeneous entity that is enriched in NUP98 fusions, with the pure erythroid subtype associated with particularly adverse outcomes.

Pure erythroid leukemia

The category of acute erythroid leukemia was significantly revised in the recently published 2016 revision to the World Health Organization (WHO) classification of myeloid neoplasms. In the previous 2008 WHO classification, acute erythroid leukemia was categorized into two subtypes: erythroleukemia and pure erythroid leukemia (PEL), whereas in the 2016 WHO update, erythroleukemia was merged into myelodysplastic syndrome, and PEL becomes the only type of acute erythroid leukemia. PEL is a rare and aggressive form of acute leukemia whose biology remains poorly characterized. In this review, we discuss the clinicopathologic features, diagnosis, putative pathogenesis, and molecular biology of PEL, with an overview of novel concepts and future directions in this area.

Acute Erythroleukemias, Acute Megakaryoblastic Leukemias, and Reactive Mimics: A Guide to a Number of Perplexing Entities

OBJECTIVES

At the 2013 Society for Hematopathology/European Association for Hematopathology Workshop, 36 cases were submitted to the session that covered acute erythroid leukemia (AEL), acute megakaryoblastic leukemia (AMKL), and reactive mimics.

METHODS

Cases were reviewed by the session chairs and workshop panel to reach a consensus diagnosis.

RESULTS

For acute erythroleukemia, erythroid/myeloid type, discussion acknowledged overlapping features between AEL and myelodysplastic syndromes. Cases submitted as pure erythroid leukemia had distinctive morphology and immunophenotype, complex karyotypes, and aggressive clinical behavior, illustrating certain diagnostic features not currently captured by the current World Health Organization (WHO) definition. In Down syndrome, there were striking similarities between transient abnormal myelopoiesis and AMKL. Most cases of AMKL in adults would be classified as acute myeloid leukemia with myelodysplasia-related changes according to the WHO classification, but this approach deemphasizes their unique clinical, morphologic, and immunophenotypic features.

CONCLUSIONS

The broad spectrum of cases illustrated the difficulties and complex issues involved in establishing a diagnosis of these entities and the need for better disease definitions.

ALDH, CA I, and CD2AP: novel, diagnostically useful immunohistochemical markers to identify erythroid precursors in bone marrow biopsy specimens

Neoplastic erythroid proliferations may represent a diagnostic challenge owing to the difficulty in characterizing immature erythroblasts. Immunohistochemical expression of aldehyde dehydrogenase (ALDH), carbonic anhydrase isoenzyme I (CA I), and CD2-associated protein (CD2AP) was assessed in 66 bone marrow biopsy specimens and compared with glycophorin A and E-cadherin. ALDH, CA I, and CD2AP labeled neoplastic erythroblasts in most acute erythroid leukemias (AELs) and myelodysplasias and highlighted benign erythroid precursors within normal marrows, erythroid hyperplasias, acute lymphoblastic leukemias (ALLs), blastic plasmacytoid dendritic cell neoplasm, and most acute myeloid leukemias (AMLs). In 2 AELs, CD2AP was negative, and 1 AML lacked identifiable ALDH+ erythroid precursors. Immature erythroblasts were strongly ALDH+, weakly CA I+, weakly CD2AP±, E-cadherin±, and weakly glycophorin A±. AML was uncommonly weakly positive for ALDH, CA I, and CD2AP, and lymphoblasts from 1 ALL were weakly ALDH+. ALDH, CA I, and CD2AP are sensitive and relatively specific immunohistochemical markers for the erythroid lineage. ALDH is superior to glycophorin A and E-cadherin in highlighting immature erythroblasts.

Acute erythroleukemia: diagnosis and management

Acute erythroleukemia is a rare subtype of acute myeloid leukemia that has undergone several changes in classification over the past 30 years. There are two subtypes of acute erythroleukemia: the more common erythroid/myeloid subtype, defined by the presence of increased erythroid cells and myeloid blasts; and the rarer, pure erythroid subtype, characterized by expansion of immature erythroid cells only. The erythroid/myeloid subtype of acute erythroleukemia is closely related to acute myeloid leukemia with myelodysplasia-related changes, and is frequently characterized by morphological dysplasia and complex karyotype. Pure erythroleukemia is a very uncommon subtype of leukemia associated with a very poor response and survival to current available therapeutic agents. Treatment results for this disease are suboptimal and new drugs are needed. This article summarizes current knowledge in the field of acute erythroleukemia.

Acute erythroid leukemia

CONTEXT

Acute erythroid leukemia (AEL) is an uncommon type of acute myeloid leukemia (AML), representing less than 5% of all cases. Acute erythroid leukemia is characterized by a predominant erythroid proliferation, and in the current World Health Organization (WHO) classification scheme there are 2 subtypes: erythroleukemia (erythroid/myeloid leukemia) and pure erythroid leukemia. Morphologic findings are most important for establishing the diagnosis. The erythroleukemia subtype, which is most common, is defined as the presence of 50% or more erythroid precursors and 20% or more blasts in the nonerythroid component. The pure erythroid leukemia subtype is composed of 80% or more immature erythroblasts. Although these morphologic criteria appear straightforward, AEL overlaps with other types of AML and myelodysplastic syndrome that are erythroid rich.

OBJECTIVE

To provide an update of AEL, including clinical presentation, morphologic features, immunophenotype, and cytogenetic and molecular data. As the erythroleukemia subtype is most common, the literature and this review are biased towards this subtype of AEL.

DATA SOURCES

Clinicopathologic, cytogenetic, and molecular information were extracted from our review of pertinent literature and a subset of AEL cases in the files of The University of Texas M. D. Anderson Cancer Center (Houston) and University of South Alabama (Mobile).

CONCLUSIONS

The current WHO criteria for establishing the diagnosis of AEL reduce the frequency of this entity, as cases once classified as the erythroleukemia subtype are now reclassified as other types of AML, particularly AML with myelodysplasia-related changes and therapy-related AML. This reclassification also may have prognostic significance for patients with the erythroleukemia subtype of AEL. In contrast, the current WHO criteria appear to have little impact on the frequency and poor prognosis of patients with the pure erythroid leukemia subtype of AEL. Molecular studies, preferably using high-throughput methods, are needed for a better understanding of the pathogenesis of AEL, and for developing diagnostic and prognostic markers.