In recent times, cancer has emerged as one of the leading causes of death in developed countries. Cancer is driven by genetic aberrations that occur spontaneously on a daily basis. The combination of genes from both parents is what gifts us intelligence, athletic ability, susceptibility to cancer, and other defining characteristics. Hereditary cancers account for a very small percentage of all cancers. A full set of genetic defects required to cause cancer may take decades to accumulate by sporadic means. Cancer-causing somatic mutations are far less dangerous than cancer-causing germline mutations. Familial cancers are caused by the accumulation of mutation events induced by environmental and lifestyle factors. The overall risk of developing such cancers depends on the common genetic makeup of individuals within a family, and how they are influenced by long-term environment and lifestyle choices. Sporadic cancers occur by sheer chance in individuals who have no known genetic risk factors or family history of cancer.