How is breast cancer passed down in families?

Familial breast ca: 2 genes are commmonly tested for called brca1 & 2. They are inherited from either male or female lines [not sex-linked], meaning history of breast cancer from both mom & dad's side are important.

Depends..: There are currently two known genes that cause breast cancer called brca1 and brca2. These genes are inherited in an autosomal dominant manner, meaning that if one of your parents has the gene you would have a 50% chance of having it as well. There are also most likely many other genes that cause breast cancer that have not yet been identified. Know you risk and speak to your doctor.