ETP all or mixed phenotype acute leukemia: Diagnostic dilemma in acute leukemia with simultaneous expression of thymic and myeloid markers

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