All-transretinoic acid (ATRA) is currently recommended as standard treatmen
t for acute promyelocytic leukemia (APL). However there has been increasing
concern that ATRA is associated with unusual sites of relapse. Although th
ere is insufficient evidence so far to substantiate this, we review the pot
ential mechanisms by which ATRA may increase the incidence of extramedullar
y and, in particular, central nervous system (CNS) relapse.