ATRA-driven differentiation process induces alteration in expression of the cell surface adhesion molecules, which could facilitate infiltration of leukemic cells into extramedullary sites.[14] However, in 2001, a study showed that ATRA did not increase the incidence of extramedullary recurrence of APL.[15] Although CD56 expression is an indicator of poor clinical outcome in patients with APL treated with simultaneous all-trans retinoic acid and chemotherapy,[16] no correlation was found with the cellular adhesion molecule CD56 in this case. Here, NCAM1 is linked to acute promyelocytic leukemia.