The causes of most childhood cancers are not known. About 5 percent of all cancers in children are caused by an inherited mutation (a genetic mutation that can be passed from parents to their children).
Most cancers in children, like those in adults, are thought to develop as a result of mutations in genes that lead to uncontrolled cell growth and eventually cancer. In adults, these gene mutations reflect the cumulative effects of aging and long-term exposure to cancer-causing substances. However, identifying potential environmental causes of childhood cancer has been difficult, partly because cancer in children is rare and partly because it is difficult to determine what children might have been exposed to early in their development. More information about possible causes of cancer in children is available in the fact sheet, Cancer in Children and Adolescents.
Information Source: http://www.cancer.gov/types/childhood-cancers
According to the National Institute of Health (http://www.cancer.gov/types/childhood-cancers), in the United States in 2015, an estimated 10,380 new cases of cancer will be diagnosed among children from birth to 14 years, and more than 1,000 children will die from the disease. Although pediatric cancer death rates have declined by nearly 70 percent over the past four decades, cancer remains the leading cause of death from disease among children. The major types of cancers in children ages 0 to14 years are acute lymphocytic leukemia (ALL), brain and other central nervous system (CNS) tumors, and neuroblastoma, which are expected to account for more than half of new cases in 2015.