Is breast cancer hereditary?

Sometimes. It is estimated that 10-15% of all breast cancer cases in the us occur due to hereditary factors. This risk may be identified by doing a simple blood test to check for brca mutations. We generally advise testing family members with known breast cancers first before checking unaffected family.
Can be. It can be, although the vast majority of women with breast cancer do not have a family history.
Majority not. Majority of breast cancer is sporadic disease. Only in about 15% could be hereditary in nature. Some other risk factors will include- dietary habits, red meat, alcohol, tobacco, sedentary, obesity, hormones use, previous radiation therapy to the chest wall etc.