Breast cancer is a common disease. Each year, approximately 200,000 women in the United States are diagnosed with breast cancer, and one in nine American women will develop breast cancer in her lifetime. But hereditary breast cancer – caused by a mutant gene passed from parents to their children – is rare. Estimates of the incidence of hereditary breast cancer range from between 5 to 10 percent to as many as 27 percent of all breast cancers.
In 1994, the first gene associated with breast cancer – BRCA1 (for BReast CAncer1) was identified on chromosome 17. A year later, a second gene associated with breast cancer – BRCA2 – was discovered on chromosome 13. When individuals carry a mutated form of either BRCA1 or BRCA2, they have an increased risk of developing breast or ovarian cancer at some point in their lives. Children of parents with a BRCA1 or BRCA2 mutation have a 50 percent chance of inheriting the gene mutation.
Not all hereditary breast cancers are caused by BRCA1 and BRCA2. In fact, researchers now believe that at least half of hereditary breast cancers are not linked to these genes. Scientists also now think that these remaining cases of hereditary breast cancer are not caused by another single, unidentified gene, but rather by many genes, each accounting for a small fraction of breast cancers. In Learning About the BRCAX Study, researchers discuss a recent advance in understanding hereditary breast cancer, and the challenges that remain.
***Above Information is an excerpt from the National Institute of Health, National Human Genome Research Institute. To read more, please visit Genome.gov