Affiliation:
1. Department of Laboratory Hematology, SRL Reference Lab, Mumbai, Maharashtra, India,
Abstract
Early T precursor acute lymphoblastic leukemia (ETP ALL) is rare and has a characteristic phenotype. Mixed phenotype acute leukemia (MPAL), as per World Health Organization, needs to have two different lineages. On cytochemistry, myeloid lineage is designated by more than 3% blast cells positivity for cytochemical myeloperoxidase (MPO). Flow cytometric analysis of MPO an arbitrary cutoff of 10% has been described in the literature for this purpose by some authors. Many laboratories performing flow cytometric immunophenotyping of hematolymphoid neoplasms do not use cytochemical MPO. The differential diagnosis between ETP ALL with myeloid antigen expression and T/Myeloid MPAL is tricky. Here, we describe a case where in cytochemistry and morphology favor myeloid lineage and flow cytometry findings in isolation favored ETP ALL, thereby highlighting the benefits of cytochemical MPO staining of bone marrow/blood smears in the diagnostic workup for acute leukemia.