In general, in the setting of a case of AML with myeloid and B-cell antigen expression, a history of myelodysplasia or cytotoxic therapy, the demonstration of pDC differentiation by flow cytometry, and the presence of a RUNX1 lesion (mutation, copy number gain, and/or translocation exclusive of a rearrangement with RUNX1T1) may favor a diagnosis of AML with a RUNX1 lesion over a diagnosis of MPAL-B/myeloid. The gene discussed is RUNX1T1; the disease is Myelodysplasia.