Adult mixed phenotype acute leukemia (MPAL): B/myeloid MPALisoMPO is distinct from other MPAL subtypes.

Olga K Weinberg, Jake Dennis, Hamid Zia, Pu Chen, Andrew Chu, Prasad Koduru, Hung S Luu, Franklin Fuda, Weina Chen

International journal of laboratory hematology 2023 Apr

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Myeloperoxidase (MPO) is considered a specific marker of myeloid/non-monocytic lineage in the diagnosis of mixed phenotype acute leukemia (MPAL). However, the clinical significance of isolated dim MPO expression in otherwise typical B lymphoblastic leukemia (B-ALL; referred to as B/myeloid MPALisoMPO ) in adult patients is unknown. We compared flow cytometric immunophenotype and clinicopathological findings among cases of B/myeloid MPALisoMPO (n = 13), other MPAL subtypes (n = 10, B/myeloid and T/myeloid MPAL), B-ALL (n = 64), and acute myeloid leukemia (AML, n = 58), using the 2016 WHO classification. For MPAL cases, MPO was reported as the percent of MPO positive blasts and its intensity (dim or moderate/strong). The pattern of heterogenous antigen expression (inversely coordinated expression between myeloid and lymphoid markers and cell size) was assessed. Cases of B/myeloid MPALisoMPO showed a fairly homogenous single B-lineage blast population with dim MPO expression whereas cases of other MPAL subtypes displayed heterogeneous antigen expression and moderate/strong MPO expression. The percent of MPO positive blasts in these two groups was similar. Expressions of CD15, CD117, and monocytic markers were more common in other MPAL than in B/myeloid MPALisoMPO . B/myeloid MPALisoMPO patients had similar overall and leukemia free survivals as B-ALL patients and better than other MPAL patients. This is the first study to investigate the clinical significance of adult B/myeloid MPALisoMPO using the 2016 WHO classification. Our results suggest that B/myeloid MPALisoMPO clinically behaves more similarly to B-ALL than to other MPAL subtypes, supporting the 2016 WHO classification to segregate this entity from other MPAL subtypes. © 2022 John Wiley & Sons Ltd.

Citation

Olga K Weinberg, Jake Dennis, Hamid Zia, Pu Chen, Andrew Chu, Prasad Koduru, Hung S Luu, Franklin Fuda, Weina Chen. Adult mixed phenotype acute leukemia (MPAL): B/myeloid MPALisoMPO is distinct from other MPAL subtypes. International journal of laboratory hematology. 2023 Apr;45(2):170-178