Pathophysiology
Breast cancer, like other forms of cancer, is the outcome of multiple environmental and hereditary factors. Some of these factors include:
- Inherited defects in DNA repair genes, such as BRCA1, BRCA2 and TP53.
- Lesions to DNA such as genetic mutations. Mutations that can lead to breast cancer have been experimentally linked to estrogen exposure.
- Failure of immune surveillance, a theory in which the immune system removes malignant cells throughout one's life.
- Abnormal growth factor signaling in the interaction between stromal cells and epithelial cells can facilitate malignant cell growth.
People in less-developed countries report lower incidence rates than in developed countries.
In the United States, 10 to 20 percent of patients with breast cancer and patients with ovarian cancer have a first- or second-degree relative with one of these diseases. Mutations in either of two major susceptibility genes, breast cancer susceptibility gene 1 (BRCA1) and breast cancer susceptibility gene 2 (BRCA2), confer a lifetime risk of breast cancer of between 60 and 85 percent and a lifetime risk of ovarian cancer of between 15 and 40 percent. However, mutations in these genes account for only 2 to 3 percent of all breast cancers.
