Check your family history

Tell your doctor if any of your close relatives have ever been diagnosed with cancer.
A family sitting together on a couch.

Learn what you can about your family history of cancer

In some families, certain abnormal genes that cause cancer can be passed down from parent to child. These abnormal genes may lead to people in that family having cancer. But this is not as common as you might think. There are also other reasons why cancer may happen in many members of a family, including sharing a common environment or lifestyle.

A family sitting together on a couch.

Learn what you can about your family history of cancer. Talk to your doctor about it. Make sure to tell your doctor if your parents, children, brothers or sisters have ever had cancer. Your doctor will want to know what type of cancer these close relatives had and their age when they were diagnosed. 

Your doctor can help you understand your cancer risk and talk to you about possible next steps, such as genetic testing.

All about genes

We all inherit a set of genes from each parent. These genes are responsible for traits such as how tall you are, the shape of your body and the colour of your hair, eyes and skin. People from the same family often share many other types of characteristics.

What are genes?

Our bodies are made up of cells. In each and every cell, genes guide how the cell develops and functions. Every gene has a specific role. Genes are like a huge instruction manual for our bodies, determining what we look like and how our bodies will grow and function.

What are gene mutations?

A gene mutation happens when there is a change or mistake in a gene.

Gene mutations can happen in 2 ways: 

Are gene mutations always harmful?

A gene mutation can be harmful, harmless or even helpful.

For most mutations, a cell can usually repair any damage before it becomes a problem. But if it can't repair the damage, certain mutations can lead to a cell becoming a cancer cell. Cancer cells grow and divide in an uncontrolled way.

Inheriting a harmful gene mutation may increase your risk for cancer. It does not mean you will definitely develop cancer.

Genes and cancer risk in families

When there is cancer in your family, it’s normal to worry that you will develop cancer as well. But even if 1 or 2 family members have been diagnosed with cancer, it doesn’t mean that you will. This is especially true if the family member is not a first-degree relative (your parent, child or sibling) or if the cancers are of different types.

How do I know if the cancer in my family is hereditary?

Only about 5 to 10% of all cancer cases are hereditary, meaning they are caused by an inherited gene mutation.

A cancer might be considered hereditary if:

  • the cancer has developed in more than 1 generation
  • family members developed cancer when they were younger than 50 years old or at a younger age than usual for that type of cancer
  • family members have each had more than 1 type of cancer

There are genetic tests available to test for gene mutations for some types of cancer. Genetic testing should always be done at a clinic that also provides counselling and education. Some people may decide not to have genetic testing because they prefer to not know if they are at increased risk of cancer or other inherited diseases.

What can I do if I have increased risk of developing cancer because of my family history?

Depending on how high your risk is, cancer specialists may recommend ways to help prevent or detect cancer early.

Your options may include:

  • changing your lifestyle
  • having genetic testing
  • having regular checkups
  • beginning screening at an earlier age or having screening tests more often
  • having preventive surgery
  • taking drugs that may help lower risk

Do I need to tell my kids?

It’s important for your children to know about their family health history. If you or other family members have had genetic testing that found a gene mutation, your children may also choose to get tested when they are older.

Which cancers are hereditary?

Scientists have discovered inherited gene mutations for certain types of cancer, including:

  • adrenal gland cancer
  • bone cancer
  • brain and spinal cord cancers
  • breast cancer
  • colorectal cancer
  • eye cancer (melanoma of the eye in adults and retinoblastoma in children)
  • fallopian tube cancer
  • kidney cancer, including Wilms tumour in children
  • some types of leukemia and lymphoma
  • hepatoblastoma (a rare type of liver cancer that affects children)
  • neuroblastoma
  • neuroendocrine tumours
  • oropharyngeal cancer
  • ovarian cancer
  • pancreatic cancer
  • parathyroid gland cancer
  • pituitary gland cancer
  • prostate cancer
  • rhabdomyosarcoma
  • skin cancers
  • small intestine cancer
  • soft tissue sarcoma
  • stomach cancer
  • testicular cancer
  • thyroid cancer
  • uterine cancer

Some gene mutations increase the risk of developing more than one type of cancer. For example, a gene mutation that increases a woman’s risk of developing breast cancer may also increase her risk of ovarian cancer.

Inherited gene mutations are often linked to a family cancer syndrome. Most are rare. Not everyone with a family cancer syndrome develops cancer.

Research is continuing to tell us more about specific genes that may put people at higher risk of developing these and other types of cancer.