[Dentigerous cyst in a pediatric patient with acute lymphoblastic leukemia type 1].

Objective: To report medical and surgical treatment in a patient with acute lymphoblastic leukemia type 1 who developed a dangerous cyst.

Clinical Case: A male of 8 years with acute lymphoblastic leukemia type 1, whose treatment was in induction. In one month, the patient presented a facial asymmetry due to mandibular growth and acute pain, hyperthermia and malaise.