Oncologists and cancer biologists are frequently confronted by the question of what causes cancer? This is particularly vexing for cancers affecting children and young adults who have had limited exposure to environmental mutagens and the effects of aging. Here, I focus on a general framework of the causes of early-onset cancer development in children and young adults by relating inherited and constitutional cancer predisposition, oncogenic pathogens, and developmental mutations. This framework has implications not only for mechanistic investigation of young cancers, but should also clarify improved strategies for their treatment, screening, and potential prevention.
