Many families have more than one member who has developed cancer. This can be because of shared risk factors such as obesity or smoking, but may also be because these family members share a genetic risk.
Cancer is described in three main ways: as sporadic, familial, or hereditary. Each type has its own risks and appears in different ways.
Sporadic cancer is the type that occurs by chance, and is the most common. People who develop sporadic cancer usually do not have family members who have had the same type of cancer.
Familial cancer is caused by a combination of genetic and environmental risk factors. While people with this type of cancer may have several relatives with the same type of cancer, there is not a clear pattern of inheritance.
Hereditary cancer occurs when a gene that normally helps to prevent cancer is altered (or mutated). People with hereditary cancers are more likely to have relatives with the same type or a related type of cancer. In addition, they often develop cancer at an earlier than average age, and may also develop more than one cancer in their lifetime.
If you have a family history of cancer, or if you belong to certain at-risk populations, you may carry an altered gene in your own genetic makeup.