Most cases of breast cancer occur by chance. However, breast cancer does occur more often than usual in some families because of their genetic makeup. Genetic means that the condition is passed on through families through special codes inside cells called genes. Your genetic 'makeup' is important because the material inherited from your parents controls various aspects of your body.
This is a companion discussion topic for the original article at https://patient.info/cancer/breast-cancer-leaflet/breast-cancer-risk-factors