Your healthcare provider may look at your family’s medical history to find out if cancer runs in your family. This means that it’s hereditary. You may be asked the following questions:

Do you have a history of cancer?

How many people in your family have cancer?

What type or types of cancer have your family members had?

Has anyone had more than 1 type of cancer?

What were their ages when the cancer started?

What is the gender of your family members with cancer?

Are the cancers unilateral or bilateral? This means does the cancer affect just 1 side of the body or both. For instance, cancer was found in both kidneys.

What type of environmental exposures or lifestyle risks do the family members with cancer have that might be linked to their risk for cancer. For instance, are they smokers?

How are the people with cancer related to one another?

Is there a vertical pattern of inheritance? For instance, are there parents with cancer who have children with cancer?

What is the ancestry and ethnicity of your family?

This information is recorded in a form of a family tree called a pedigree. Many times, other information, like medical records or the results of genetic testing, are requested.

All this information is used to try to classify your family history into 1 of 3 categories. These include sporadic, familial, and inherited. These help to find out:

If your relatives have an increased chance of getting certain types of cancer

How great the risk of cancer might be

If genetic testing might help you learn more about cancer risks in your family

Sporadic cancer

The word sporadic means to happen by chance. Most cancers are sporadic cancers. They’re caused by gene changes that take place in 1 cell that, with time, are passed on to new cells and can lead to cancer.

Families who have few people with cancer at an older age are often classified as sporadic. In other words, there’s no inherited pattern of cancer present. This may be the case if there are 1 or 2 people in your family who have cancer at a typical age of onset. Because cancer is common, this isn’t abnormal.

With sporadic cancers, relatives are often at normal but not increased cancer risk. Genetic testing is often not helpful in these families.

Familial cancer

Familial cancer is when there are more people with cancer in your family than chance alone would predict. And these cancers often happen at a younger age than expected. This may mean there’s a gene mutation passed on in your family that increases the risk for cancer. But it could also be a sign of shared environmental or lifestyle factors. For instance, if there seems to be a lot of lung cancer among older family members who smoke, the cause is more likely smoking than an inherited gene change.

In general, with familial cancer, close relatives have a modestly increased risk of developing the cancer in question. There’s a small chance that genetic testing will help to further assess cancer risks.

Inherited cancer

Inherited cancer is when you have many family members with the same or related cancers. The cancers tend to happen at younger than average ages, often younger than age 50. These cancers are more likely to affect both organs of a pair, like cancer in both kidneys or in both breasts.

There’s also often a history of family members who have had 2 or more kinds of cancer. For instance, ovarian cancer in a breast cancer survivor. Here are some facts about inherited cancer.

Inherited cancer is linked to a changed gene (or gene mutation) that increases the risk of certain types of cancer. The mutation is found in every cell in the body. By itself, it doesn’t cause cancer. But other random mutations added to it lead to cancer.

These cancers are rare. Fewer than 1 in every 100 people with cancer can link it to an inherited gene.

Families with inherited cancer often have cancer in 2 or more generations.

When a parent has an inherited gene mutation, each child has a 1 in 2 chance of inheriting it.

People in the family who inherit the mutated gene have a high chance of developing the cancer(s) linked to it.

Those who do not inherit the mutated gene are not at increased cancer risk.

Genetic testing isn’t right for everyone. But it can often be helpful in figuring out who in the family has an increased cancer risk. In most cases, it’s important to test a relative with cancer first to see if a gene mutation can be found. Identifying the mutation can help in making decisions about testing relatives who have not had cancer. It’s always best to talk with a genetic counselor before doing genetic testing.