If you are under the age of 45, you may have a higher risk for breast cancer if—
• You have close relatives who were diagnosed with breast cancer before the age of 45 or ovarian cancer at any age, especially if more than one relative was diagnosed or if a male relative had breast cancer.
• You have changes in certain breast cancer genes (BRCA1 and BRCA2), or have close relatives with these changes, but have not been tested yourself.
• You have Ashkenazi Jewish heritage.
• You received radiation therapy to the breast or chest during childhood or early adulthood.
• You have had breast cancer or certain other breast health problems, such as lobular carcinoma in situ (LCIS), ductal carcinoma in situ (DCIS), atypical ductal hyperplasia, or atypical lobular hyperplasia.
• You have been told that you have dense breasts on a mammogram.
The latter (last bullet point) is typically true for younger women whether they have been told that they have dense breasts or not. This is also why self advocacy is so important as well as knowing your family history.