percent of childhood cancers. Peak incidence is at age 15, a trend that coincides with adolescent growth spurts. Osteosarcoma is the most common cancer in this category, which in children often occurs in the bones around the knee. Ewing’s sarcoma is a rare bone cancer that usually occurs in adolescence and is more common in girls than boys. Five-year survival rates have improved substantially over time, to 65 percent for osteosarcoma and 59 percent for Ewing’s sarcoma.

8. Sympathetic and allied nervous system tumors. Cancers in this category account for 5 percent of childhood cancers and are the most common cancers diagnosed in the first year of life. Neuroblastoma accounts for virtually all cases of cancer in this category. Neuroblastoma is a solid cancerous tumor that begins in nerve tissue in the neck, chest, abdomen, or pelvis, but usually originates in the abdomen in the tissues of the adrenal gland. By the time it is diagnosed, the cancer usually has metastasized, most commonly to the lymph nodes, liver, lungs, bones, and bone marrow. Two- thirds of children with neuroblastoma are diagnosed when they are younger than 5 years of age. Although neuroblastoma may be present at birth, it does not always proceed to become an invasive malignancy, a circumstance unique to neuroblastoma. In contrast with CNS malignancies, survival is highest among infants under 1 year of age, and declines with increasing age. Overall, the 5-year survival rate for children with sympathetic and allied nervous system tumors has improved to 66 percent.

9. Renal tumors. Renal tumors account for 4 percent of childhood cancers. Wilms’ tumors account for more than 90 percent of malignancies of the kidney among children and adolescents, usually affecting those under age 5. Wilms’ tumor may involve one or both kidneys. Between 1975 and 1997, 5-year survival rates improved for Wilm’s tumor, rising from 81 percent to 91 percent

10. Retinoblastoma. Accounting for 2 percent of childhood cancers, retinoblastoma is a rare tumor involving the retina of the eye, or sometimes the pineal gland. Although retinoblastoma may occur at any age, it most often occurs in younger children, usually before the age of 5 years. The tumor may be in one or both eyes. Retinoblastoma is usually confined to the eye and does not spread to nearby tissue or other parts of the body. Retinoblastoma may be hereditary or nonhereditary. The hereditary form may occur in one or both eyes, and generally affects younger children. Most cases of retinoblastoma that occur in only one eye are not hereditary and are found more often in older children. When the disease occurs in both eyes, it is always hereditary. Five-year survival rate is about 94 percent and has not changed over the past two decades.

11. Hepatic tumors. A rare malignancy in childhood, liver tumors account for just over 1 percent of childhood cancers. More than two-thirds

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