ETP/Myeloid Mixed Phenotype Acute Leukemia: A Provisional Entity

Excerpt

ETP-ALL is a newer entity incorporated in the 2017 WHO revised classification of hematolymphoid neoplasms characterized by expression of one or more stem cell/myeloid antigens such as CD34, CD33, CD13, HLA-DR, CD117, CD65, CD11b etc. in addition to the T cell antigens and lack CD1a, CD8 and CD5 (ma be dim to negative). By definition, MPO is negative. If MPO is positive in the presence of ETP-ALL immunophenotype, it must be characterized as T/myeloid MPAL [1]. A new provisional entity, ETP-myeloid MPAL has been proposed recently in addition to the already existing ETP ALL by Patel et al. on the basis of significant overlap between the immunophenotype (CD117, CD13 and CD33 positive) and molecular profiling (higher frequency of DNMT3 and FLT3 mutations) of these patients [2], hence supporting the notion of lymphocyte-primed multipotent progenitors due to promiscuity between immature precursor T cells and myeloid lineages. We report 2 such cases which fall in the domain of ETP-myeloid MPAL (Table 1; Figs. 1, 2, 3).

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