Case of pediatric acute promyelocytic leukemia presenting as extramedullary tumor of the mandible.

BACKGROUND Acute promyelocytic leukemia (APL) is a malignant subtype of acute myeloid leukemia caused by the PML-retinoic acid receptor (RAR)α fusion gene. APL may be discovered in adulthood and diagnosed after spontaneous gingival bleeding or difficulty in hemostasis after oral surgery such as tooth extraction. However, APL is extremely rare in children. METHODS AND RESULTS A 1-year-old boy presented with a mass on the mentum of the mandible. The marked periosteal reaction was seen on CT and MRI, leading to strong suspicion of a malignant bone-derived tumor such as a sarcoma. Chromosome banding by fluorescence in situ hybridization (FISH) showed PML-RARα, confirming the diagnosis of APL. Treatment with tretinoin was immediately initiated. No signs of recurrence have been noted 1 year after treatment. CONCLUSIONS We report herein a rare case involving an infant with APL who presented with an extramedullary tumor of the mandible, whom we treated with good results.