A term used to describe cancers that occur between birth and 15 years of age. Childhood cancers are very rare and may differ from adult cancers in the way they grow and spread, how they are treated, and how they respond to treatment. Common types of childhood cancer include leukemia (begins in blood-forming tissue such as bone marrow), lymphoma (begins in the cells of the immune system), neuroblastoma (begins in certain nerve cells), retinoblastoma (begins in the tissues of the retina), Wilms tumor (a type of kidney cancer), and cancers of the brain, bone, and soft tissue.