Breast cancer is one of the most common forms of cancer in women in the United States. Approximately one out of every 8 American women will get breast cancer. Therefore, it is not uncommon to see more than one individual with breast cancer in a family, and to see even more in large families. The breast cancer itself is not inherited, but the increased predisposition to breast cancer can be. If the cases of breast cancer in the family are due to a gene change in either of two genes, ovarian cancer can also be seen in the family.
Genes are our bodies' instructions on how to develop and how to function.
Genes are located on the structures in the cells of our body called chromosomes. Chromosomes come in pairs, because we get one copy of each chromosome from our mother and the other copy from our father. We usually have 23 pairs, or 46 chromosomes in each cell. Since we have two copies of each chromosome, we also have two copies of the genes on those chromosomes. When these two genes function correctly, they make substances which prevent our bodies' cells from growing and dividing in an uncontrolled way.