Thinking about cancer or dealing with cancer risk can be scary or overwhelming, but we believe that receiving information and resources is comforting, empowering, and lifesaving.
Everyone has two copies of most genes, one from each parent. Most people are born with two normal copies of each gene. Hereditary cancers occur when a person is born with changes or mutations in one copy of a damage-controlling gene which normally protects against cancer. In the majority of these cases, the changes were inherited from the mother or father.
People with an inherited gene change have a 50% chance of passing the mutation to each of their children. These changes can increase the risk for cancers in different parts of the body, but they do not increase the risk for every type of cancer, and not everyone who is born with a gene change will develop cancer. The medical community uses the term "genetic susceptibility" to describe the high risk for cancer in people with an inherited mutation.
Cancer is a common disease, so most families will have some members who have had cancer but that does not mean the cancer in that family is hereditary. We don't know the cause of most cancer, but experts believe that about 10% of most cancer types are due to inherited gene changes. Cancer that does not appear to be caused by inherited genes is called "sporadic cancer." It is believed that most - perhaps 90% - of all cancers are sporadic. This means even if cancer does not run in a family, a family member can still be at risk for some type of cancer in his or her lifetime.