Are acquired gene changes passed to children?

No. Acquired gene changes, also called somatic changes, happen during a person's life and are found only in the cells where they occurred — such as tumor cells. Because they are not present in egg or sperm cells, they cannot be passed to children.

The reason comes down to which cells build the next generation. A child is built from one egg and one sperm. Whatever DNA those two cells carry gets copied into every cell of the child. Nothing else does. A change that appears in a lung cell, a colon cell, or a tumor stays in that line of cells and ends there. The National Cancer Institute puts it directly: cancer itself cannot be passed from parents to children, and genetic changes in tumor cells cannot be passed down either.

Acquired changes arrive two ways. Random mistakes happen as cells multiply, and cells multiply constantly. DNA is also damaged by carcinogens in the environment, such as chemicals in tobacco smoke, UV rays from the sun, and human papillomavirus. Either kind can happen at any point in life, and even in the womb. Most single changes are harmless on their own. It is the buildup over many years that can turn a healthy cell cancerous, and the vast majority of cancers form exactly that way, by chance over time.

The National Cancer Institute explains that inherited changes are different. An inherited change can be passed on because it is present in a parent's egg or sperm cell, and so it ends up in every cell of the child's body. Up to 10% of all cancers may be caused by inherited genetic changes.

This is why the changes found in a tumor generally do not carry risk for relatives, while an inherited change can. The distinction shows up as two entirely different tests, and mixing them up is common.

Biomarker testing, also called tumor profiling or molecular profiling, is done on cancer cells. The sample is a piece of the tumor, or sometimes blood. It looks for the changes driving your cancer, and the results help your doctors choose a therapy or find a clinical trial. These are acquired changes, and they say nothing about your family.

Genetic testing for inherited cancer risk is done on normal cells instead. It usually uses a small blood sample, though saliva, cheek cells, or skin cells can work. This is the test that speaks to your relatives.

Occasionally a tumor test uncovers a change that a person was actually born with; a separate inherited-risk test can confirm whether it is truly inherited, which is what would matter for family members. So if a report mentions a gene you recognize, such as BRCA1 or BRCA2, ask which test produced it and on what sample.

Two practical notes. Fear of insurance trouble keeps people from testing, so it is worth knowing that the Genetic Information Nondiscrimination Act of 2008 and the HIPAA Privacy Rule prohibit discrimination based on genetic test results, though your health insurer does have legal access to your medical records. And at-home genetic tests are not generally recommended for judging inherited cancer risk. They carry real drawbacks, and a genetic counselor is the right person to sort out what any result actually means for you and your family.