Family history

Certain cancers, such as breast cancer, ovarian cancer, prostate cancer, colorectal cancer, retinoblastoma and neuroblastoma, can occur in families. A family history of these cancers can increase a person’s cancer risk, especially if the cancer occurred in a first-degree relative (parent, sibling or child). If members of a family develop a certain cancer, it doesn’t necessarily mean that someone else in the family will also get cancer. This is especially true if the family member was not a close blood relative or was diagnosed at an older age.

Sometimes more members of a family than would be expected by chance develop cancer. Many different factors can affect a family’s pattern of cancer. Cancer can develop due to chance or similar lifestyle factors of family members. It can also be related to a specific gene mutation, passed from parents to children (inherited), that makes family members more prone to developing certain cancers.

A person with no family history of cancer may still be at risk of developing cancer. Only a small number of cancers (5%–10%) are hereditary. Most cancers (about 90%) are not hereditary and happen by chance (sporadic) during a person’s lifetime.