“…MPO stands as the most robust marker that will identify myeloid engagement. Recent publications have redefined the threshold for MPO positivity, 5,6 and yet most MPAL cases with a myeloid component will express MPO broadly in most blasts. An alternative, for MPAL with a strong monocytic differentiation, is represented by (very rare) cases in which blasts will be positive for nonspecific esterase and/or express at least two of the following antigens: CD14, CD11c, CD36, CD64, or cytoplasmic lysozyme.…”