Acute lymphoblastic leukemia (ALL) is the most frequent malignancy in children, representing 25% of all the neoplastic diseases in people younger than 15 years .
The peak of incidence is between ages 2 and 3 years . In adolescents (15 to 19 years), ALL comprises only 7% of all cancers . In the United States, it is estimated that 2500 – 3500 children are diagnosed with ALL every year . The incidence appears to be increasing. In Europe it was reported a 1.4% increase in incidence from 1970 to 1999 .