Background: Mixed-phenotype acute leukemia (MPAL) is a rare but difficult to treat hematologic malignancy with immunophenotypic co-expression of at least two cell lineages, or with only rare cases involving all three lineages, e.g. myeloid with B-or T-lymphoid or all three of myeloid, B- and T-lymphoid altogether. Advancement in multiparametric flow cytometry has made its identification easier. The aim of this prospective study was to identify cases ofMPAL and to study the incidence, clinical features, hematological profile and immunophenotypic expression profile of MPAL at our center.
Methods: All consecutive cases of acute leukemia (AL) from November 2015 to December 2019, diagnosed on the basis of bone marrow and/or peripheral blood morphology were utilized for immunophenotyping. A panel of fluorochrome-labelled monoclonal antibodies against myeloid, B-cell, T-cell and immaturity markers were used. Monoclonal Antibodies used were: CD45, CD34,TdT, HLA-DR, Anti-MPO, CD13,CD33, CD117, CD3, CD5,CD7,CD19,CD79a, CD22, CD10. These cases were diagnosed based on immunophenotyping of EDTA peripheral blood or bone marrow aspirates to have MPAL as per the World Health Organization (WHO) 2008 guideline.
Results: Among 616 consecutive AL cases diagnosed and evaluated during this period, 22(3.57%) patients with MPAL were identified fulfilling WHO 2008/ EGIL criteria for immunophenotypic characteristics of AL. Fourteen were adults, male: female = 5:2. Eight were children, male: female= 3:1. Median age of this cohort (n=22) was 23.5 years (range: 1 -70 years). Fifteen (68.18%) cases were diagnosed as B/myeloid, 5(22.72%) as T/myeloid and 2 (9.1%) as B/T MPAL. Morphologically MPAL cases were diagnosed as 15 acute myeloid leukemia (AML) and 7 acute lymphoid leukemia (ALL) where as blast morphology was not predictive of a MPAL.
Conclusion: Multiparametric flow cytometry by using comprehensive panel of monoclonal antibodies is a valuable tool to diagnose MPAL as it is a rare subset of acute leukemia known to have a poor outcome.
Keywords: MPAL, Acute leukemia, Flow cytometry, Immunophenotyping, WHO, EGIL