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.