From The National Cancer Institute Among the 12 major types of
childhood cancers, leukemias (blood cancers) and cancers of the
brain and central nervous system account for more than half of
the new cases. About one-third of childhood cancers are
leukemias. The most common type of leukemia in children is acute
lymphoblastic leukemia. The most common solid tumors are brain
tumors(e.g., gliomas and medullo blastomas), with other solid
tumors (e.g., neuroblastomas, Wilms tumors, and sarcomas such as
rhabdomyosarcoma and osteosarcoma) being less common.