All cancer is genetic, but only some cancer is hereditary. Cancer occurs when the normal mechanisms that control cell growth fail because of a genetic mutation. Without proper control mechanisms, healthy cells can grow too rapidly or fail to correct changes, leading to cancer. Some people are born with mutations inherited from a parent; others acquire a mutation during their lifetime.
In fact, for most people with cancer, the cancer-causing gene mutations result from acquired changes that happen over the course of a lifetime. Acquired mutations commonly arise in the natural process of aging or due to environmental factors, such as sun exposure or smoking. These mutations happen randomly and are not passed down from parents to children. Cancer caused by acquired mutations is called sporadic cancer.
On the other hand, hereditary cancers can occur when individuals are born with an inherited genetic mutation that predisposes them to an increased risk for cancer. While not everyone with an inherited genetic mutation will develop cancer, the risk is significantly increased compared to the average population risk. A person with an inherited gene mutation also has a 50% chance of passing it down to each child.