The differentiation of an AML, particularly an epithelioid AML, from a melanotic Xp11 TRC is mainly based on the former tumor’s immunoreactivity for MiTF, a muscle marker (SMA) and melanocytic markers (HMB45 and Melan A) and the latter tumor’s immunohistochemical negativity for MiTF and SMA and positivity for HMB45 in a patchy pattern. The gene discussed is SMN1; the disease is acute myeloid leukemia.