Before you decide that cancer runs in your family, first gather some information. For each case of cancer, look at:
Who is affected? How are we related?
What type of cancer is it? Is it rare?
How old was this relative when they were diagnosed?
Did this person get more than one type of cancer?
Did they smoke?
Cancer in a close relative, like a parent or sibling (brother or sister), is more cause for concern than cancer in a more distant relative. Even if the cancer was from a gene mutation, the chance of it passing on to you gets lower with more distant relatives.
Breast cancer is a cancer that can be hereditary. A family history of breast cancer does put you at increased risk for breast cancer. A woman who has a first-degree relative (such as a mother, sister, or daughter) with breast cancer is about twice as likely to develop breast cancer as a woman without a family history of this cancer. Still, most cases of breast cancer, even those in close relatives, are not part of a family cancer syndrome caused by an inherited gene mutation.
The chance that someone has an inherited form of breast cancer is higher the younger they are when they get the cancer and the more relatives they have with the disease. Inherited breast cancer can be caused by several different genes, but the most common are BRCA1 and BRCA2. Inherited mutations in these genes cause hereditary breast and ovarian cancer syndrome (HBOC). Along with breast and ovarian cancer, this syndrome can also lead to male breast cancer, pancreatic cancer, prostate cancer, as well as some others. This syndrome is more common in women of Ashkenazi descent than it is in the general U.S. population.
This is why it is so important for you to have an early detection plan. You can creaste a plan at www.earlydetectionplan.org. This plan takes into account your risk profile and age. Of course, if you notice any changes in your breasts, you should consult your physician.