There are no hard biological data available concerning APL CNS localization, although it has been associated with several factors including high WBC count (>10 × 109/L), CNS hemorrhage, expression of CD2, and/or CD56 in blasts, PML-RARA bcr3 isoform, differentiation syndrome, and above all induction therapy with single agent ATRA and regimens without Cytarabine [120,121,122]. Here, NCAM1 is linked to acute promyelocytic leukemia.