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 5 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 62 . The median is the middle value of a group of numbers, so about half of the women were diagnosed before age 62 and about half were diagnosed after age 62.
The median age of diagnosis varies by race and ethnicity.
For example, black women tend to be diagnosed at a younger age than white women . The median age at diagnosis for black women is 59, compared to 63 for white women .
Learn more about race, ethnicity and breast cancer risk.
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 . However, the median age of diagnosis varies by race and ethnicity.
For example, black men tend to be diagnosed at a younger age than white men .
The median age at diagnosis for black men is 65, compared to 68 for white men .
Learn more about breast cancer in men.
The older we get, the more likely it is abnormal changes will occur in our cells. When many of these changes occur, cancer can develop.
Data source: SEER 2010-2014 
Note: Though this graph shows a rate of 0 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.