ASK DR MIRIAM.
QI'm in my mid 30s and my aunt (my mother's sister) has developed breast cancer. I'm worried that breast cancer may run in the family.
A All cancers are caused by changes (mutations) in genes and most cancers develop because these happen during a person's lifetime, so not inherited from a family member.
Diet, smoking and sunlight can cause gene mutations as well as getting older.
When there's a cancer gene in the family there will be generations which hasn't happened in your family. But even inheriting a gene doesn't mean you'll get cancer, it just means you have an increased risk of developing certain types of cancer.
If you don't have at least two relatives with the same type of cancer on the same side of your family it's unlikely you've inherited a cancer gene.
Only a small proportion of cancers, up to five out of a 100, are clearly linked to an inherited cancer gene, but please see your doctor and discuss your anxiety.