Breast Cancer Susceptibility Genes BRCA1 and BRCA2

Breast cancer is the most common cancer affecting women in the United States. There are at least two major genes (BRCA1 and BRCA2) that cause breast cancer when they mutate. These genes are inherited from parent to child, and parents increase the risk of cancer of children who have these genes. The BRCA1 and BRCA2 genes are located on chromosome 17 and chromosome 13, respectively. For women with these mutations, the likelihood of developing breast cancer is 90%. In contrast, men carrying BRCA1 are not at risk of breast cancer, but men carrying the BRCA2 gene are at higher risk.

Two breast cancer susceptibility genes were recently discovered. The first one is BRCA1 (deficiency of this gene is common in people with breast cancer), and the second one is BRCA2 (the deficiency of this gene is only related to breast cancer). People whose BRCA1 gene is mutated have a risk of developing breast cancer at the age of 70 with 66%. Women are 100 times more likely to develop breast cancer than men. More than 80% of breast cancer occurs in women over 50 years old. At the age of 40, her odds are 127 (217), but for women under 30, they account for only 1.5% of all cases of breast cancer. Approximately 5% of all breast cancers are hereditary. Those with a family history of breast cancer among first-degree relatives (ie mothers, sisters, and daughters) are 2 to 3 times more likely to be in the general population

The discovery of the BRCA1 and BRCA2 genes associated with the early onset of breast cancer allows women with a family history of early breast cancer to detect mutations in these genes. Only 5 to 10 percent of breast cancers show genetic evidence. Of these, 45% were associated with the BRCA1 mutation and 35% were associated with BRCA2. The remaining 20% ​​of the gene is still unknown. If the BRCA1 and BRCA2 tests are negative, there is no evidence that women develop breast cancer due to these mutations. However, due to these or other somatic mutations of genes, she may develop breast cancer. If the BRCA1 or BRCA2 test is positive, other families will be tested to determine if the gene is hereditary. If other families are negative, the risk of disease increases for those with mutations, but the genetic risk of this type of cancer is less.