Mixed phenotype acute leukemia (MPAL) represents approximately 3–5% of all acute leukemia cases and is defined by blast populations that co-express markers from more than one hematopoietic lineage. In most cases, blasts exhibit myeloid markers together with either B-cell or T-cell markers. The rarest subtype is mixed B/T acute leukemia. We report the case of a 7-year-old boy who presented with weakness and fatigue and was diagnosed with MPAL, not otherwise specified, B/T rare type, based on bone marrow examination and immunophenotyping. This case highlights the essential role of comprehensive immunophenotyping in establishing an accurate diagnosis of MPAL. Given the limited information in the literature, case series and prospective studies are needed for a better understanding and successful treatment.
