Familial and genetic factors are identified in 5-15% of childhood cancer cases. In <5-10% of cases, there are known environmental exposures and exogenous factors, such as prenatal exposure to tobaccoX-rays, or certain medications.[9]For the remaining 75-90% of cases, however, the individual causes remain unknown.[9] In most cases, as in carcinogenesis in general, the cancers are assumed to involve multiple risk factors and variables.[10]
https://emedicine.medscape.com/article/989841-overview
Approximately 1.69 million new cases of invasive cancers are diagnosed annually in the United States. Cancer is the second leading cause of death in the United States among children age 1 to 14 years and there are an estimated 10,270 cases annually in this age group. [1] The heterogeneity of pediatric cancer is substantial, and even the most common pediatric cancer (ie, acute lymphoblastic leukemia [ALL]) is characterized by biological and clinical diversity. As a result of this heterogeneity and low incidence, the ability of epidemiologists to ascribe causes to specific childhood cancers is extremely limited.