Breast Cancer Genetics
Most of us have heard about the BRCA1 abd BRCA2 genes and their impact on a woman's risk of developing breast and/or ovarian cancer. I have been especially thinking about this as I have met this week with two women who have been diagnosed with both malignancies. One had breast cancer several years ago and now has a new ovarian cancer diagnosis. The other received both diagnoses within a few weeks of each other.
It is important to remember that only 5%-10% of breast cancers are caused by inherited gene mutations. All the rest of us have random or sporadic breast cancers --meaning that we had some bad luck. Although increasing numbers of women are being advised to be tested (a simple blood test), the frequency is not increasing. Here is a good explanation from BreastCancer.org about breast cancer genetics. I am giving you an excerpt and then the link to read more:
BRCA1 and BRCA2 Genes
Most inherited cases of breast cancer are associated with two abnormal genes: BRCA1 (BReast CAncer gene one) and BRCA2 (BReast CAncer gene two).
Everyone has BRCA1 and BRCA2 genes. The function of the BRCA genes is to repair cell damage and keep breast cells growing normally. But when these genes contain abnormalities or mutations that are passed from generation to generation, the genes don't function normally and breast cancer risk increases. Abnormal BRCA1 and BRCA2 genes may account for up to 10% of all breast cancers, or 1 out of every 10 cases.
Having an abnormal BRCA1 or BRCA2 gene doesn't mean you will be diagnosed with breast cancer. Researchers are learning that other mutations in pieces of chromosomes -- called SNPs (single nucleotide polymorphisms) -- may be linked to higher breast cancer risk in women with an abnormal BRCA1 gene as well as women who didn't inherit an abnormal breast cancer gene.
Women who are diagnosed with breast cancer and have an abnormal BRCA1 or BRCA2 gene often have a family history of breast cancer, ovarian cancer, and other cancers. Still, most people who develop breast cancer did not inherit an abnormal breast cancer gene and have no family history of the disease.