PML and acute promyelocytic leukemia: The PML-RARa fusion is pathognomonic of acute promyelocytic leukemia (Fu et al., 1995), a subtype of acute myeloid leukemia characterized by a high response rate to all-trans retinoic acid (ATRA)/arsenic trioxide (ATO) therapy and a comparatively favorable prognosis (de Thé and Chen, 2010; Coombs et al., 2015).