The biggest single risk factor for breast cancer is age. The average age of a woman diagnosed with breast cancer is early 60s. This does not mean, however, that woman in their 50s, 40s, 30s, and even 20s do not get breast cancer. The age risk factor simply means that the older a woman gets, the greater her risk for breast cancer becomes. Also, the age risk factor does not mean that all women over 60 will get breast cancer, just that women over 60 are more likely to get breast cancer than is a woman in her 40s or 50s.