Age and female breast cancer
Age is an established risk factor for breast cancer. The older a woman is, the more likely she is to get breast cancer.
Rates of breast cancer are low in women under 40. Fewer than five percent of women diagnosed with breast cancer in the U.S. are younger than 40 . Rates begin to increase after age 40 and are highest in women over age 70 (see Figure 2.1 below). The median age of diagnosis of breast cancer for women in the U.S. is 61 .
Age is also a risk factor for breast cancer in men. The older a man is, the more likely he is to get breast cancer. However, breast cancer is much less common in men than in women (see Figure 2.1 below).
The median age of diagnosis of breast cancer for men in the U.S. is 68 .
Learn more about breast cancer in men.
As we get older, it becomes more likely that abnormal changes will take place in our cells. When many of these changes occur in cells, cancer can develop.
Data source: SEER 2006-2010 
Note: Though this graph shows a rate of zero in some age groups, there are a few cases of breast cancer in these age groups each year in the U.S. The numbers are too small, however, to appear on the scale used here.