Unusual sites of relapse in pre-B acute lymphoblastic leukemia

Relapses of acute lymphoblastic leukemia (ALL) in unusual sites can be challenging to diagnose. We present unusual relapses occurring in children with ALL treated in a single institution over a 22-year period. Of 172 relapses, 9 (5.2%) were at unusual sites (nonmarrow, testes, central nervous system). The most common site of relapse was ocular (66%). The median symptom-to-diagnosis interval was 20 days. Two of 9 children attained second remission. A possibility of relapse should be considered when evaluating unusual symptoms in a child with underlying ALL.