Clinical and Molecular Characteristics of Patients with Mixed Phenotype Acute Leukemia

Introduction: Mixed phenotype acute leukemia (MPAL) is a rare heterogeneous disease with a poor prognosis. This study analyzed the clinical, immunophenotypic, molecular, and cytogenetic characteristics of a group of patients with MPAL. Methods: This prospective study included 75 patients diagnosed with MPAL according to the World Health Organization (WHO)-2016 diagnostic criteria, using cytochemistry, conventional cytogenetics, and molecular studies. Screening of BCR::ABL1 fusion gene was performed by Fluorescent in-situ hybridization (FISH) and polymerase chain reaction (PCR). Results: Children represented 49.3% of MPAL patients. The main phenotype was B-lymphoid/myeloid (80%). Molecular alterations were detected in 17 patients (22.7%). The BCR::ABL1 fusion gene was detected in 10 patients (13.3%).. Myeloid protocols were used to treat 58 patients (77.3%), and lymphatic protocols in 17. By the end of the follow-up, 57 patients (76%) achieved complete remission (CR). There was no association between BCR::ABL1 and response to treatment. The cumulative overall survival (OS) at 12 months was 47.8%. The bone marrow transplantation (BMT) was associated with better OS (p = 0.027). The disease-free survival (DFS) was not affected by all tested prognostic factors. Conclusion: MPAL is a complex entity with heterogeneous features. BCR::ABL1 is a common abnormality. BMT is associated with better OS.