Most cancers develop as a result of a combination of risk factors, which in some cases can include family history. Some types of cancer are less likely to be genetic, such as cervical cancer and lung cancer. You should contact your GP if some close family members have developed the types of cancer mentioned above and you're worried that you might develop cancer yourself. They'll ask about your family history, and if they think there's a chance you have an increased risk of developing cancer, they'll refer you to a genetic counsellor, family cancer clinic or a cancer specialist.
Cancer Research UK has more information about family history and inherited cancer genes. Then, there are somatic changes, which means the genetic changes are only in the tumor, and not passed onto children. Whereas genetic changes that can lead to familial cancer—also called germline mutations—stem from an inherited risk from your parents. When most people hear the term genetic, they think of genes inherited from their biological mother and father. These genes are like instruction manuals, directing how your body should form and function.
With cancer, each tumor has this set of genes as well. Similarly, for cancers like leukemia, lymphoma, and multiple myeloma, the cells in the blood and bone marrow have this same set of genes. However, there can be a change—or mutation—in those genes, which leads to differences in the properties of the proteins encoded by the genes.
In some cancers, these genetic mutations are passed on from parents, which means they can be passed on to the next generation as well. These genetic changes are called mutations. If your parent has a genetic mutation, it does not mean you definitely have it too. Similarly, if you have a genetic mutation, it doesn't mean your child has it.
A parent who has one copy of a genetic mutation will pass on either the mutated gene or the normal gene. A parent can pass on the genetic mutation and increased risk even if she or he never develops cancer.
A child who does not inherit the abnormal mutation cannot pass it on. If you inherit a mutation that increases cancer risk it does not mean you are destined to get cancer. It means your risk is higher than average. Knowing you have mutation creates opportunities to decrease the risk through cancer screening and other risk-reduction measures. Learning that you have cancer, or that a close relative does, may make you think you should go online and order one of those genetic tests you may have read about or seen advertised.
That's not a wise idea. Seeing a genetic counselor will also allow you to be confident that the right tests are ordered and that the results are interpreted correctly. Genetic testing typically involves a blood or saliva sample.
A special analysis in the lab can detect DNA changes that suggest a mutation. The goal of testing is not just to get a result, but to get information that you can use to help you decrease your risk of getting cancer. For this reason, testing typically begins with the person who was diagnosed with cancer. If she or he does have a genetic mutation, it can be tested for in other family members.
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