The word sporadic means to happen by chance. Most cancers are sporadic cancers. They're caused by gene changes that take place in one cell that, with time, are passed on to new cells and can lead to cancer. Families who have a single person with cancer at an older age are usually classified as sporadic. In other words, there's no inherited pattern of cancer present. And there is often only one or two people in your family that have cancer at a typical age of onset. Relatives are usually not at increased risk of developing cancer. Genetic testing is usually not beneficial in these families.

Familial cancer is when there are more cases of cancer in your family than chance alone would predict. These cancers often happen at a younger age. And they may mean the presence of a gene mutation that increases the risk for cancer. They may also be a sign of shared environmental or lifestyle factors. For example, if there seems to be a lot of lung cancer in a family and many family members smoke, the cause is not likely an inherited gene change. In general, with familial cancer, close relatives have a modestly increased risk of developing the cancer in question. There is a small chance that genetic testing will be beneficial in further assessing cancer risks.

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

Also, there is often a history of family members who developed two or more separate cancers. For example, ovarian cancer in a breast cancer survivor. Here are some facts about inherited cancer.

• Families with inherited cancer often have cancer in two or more generations.

• When a parent has an inherited predisposition to cancer, each child has a one in two chance of inheriting the predisposition.

• People in the family who inherit the predisposition have a high chance of developing the associated cancers.

• Those who do not inherit the predisposition 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 mutation can be found. Identifying the mutation can help in making decisions about testing relatives who have not had cancer. It's best to talk to a genetic counselor before doing genetic testing.