Breast Cancer Facts

Breast Cancer Facts

Breast cancer occurs when cells in the breast begin to grow abnormally. They do not respond to regular cell growth, division, and death signals like they are supposed to. They also don’t organize normally. Instead they grow into a tumor, which may invade surrounding layers of breast tissue and possibly spread to other organs.

Although breast cancer primarily affects women, it can also occur in children and men. For the most part, the content in this section is directed at females, who make up 99 percent of all breast cancer patients. But most of the information applies to males as well.

According to the American Cancer Society (ACS), in the United States breast cancer is the second most common cancer in women (after skin cancer) and the second leading cause of cancer death in women (after lung cancer). ACS estimated that 290,170 new cases of breast cancer (in situ and invasive cancers) were diagnosed among women in this country in 2012. 

Over a woman’s lifetime, there’s a one in eight chance she will get breast cancer. For men, the lifetime risk is much lower—about one in 1,000. Breast cancer can be a highly curable disease if detected and treated early.

Breast Cancer Diagnosis

Learn about diagnostic tests used when breast cancer is suspected.

Types and Grades of Breast Cancer

Here’s an overview of some of the more common types of breast cancer—and what is meant by “grade,” “hormone-receptor positive,” and “HER2 positive.”

Stages of Breast Cancer

Find out how a cancer is classified based on its size and how far it’s spread—key factors that influence treatment.

Questions & Answers

Your questions about breast cancer answered—topics from digital mammography and hormone replacement therapy to tamoxifen and aromatase inhibitors.


The more you know about your disease, the more empowered you'll feel. This list of reputable sources about breast cancer makes gathering information easy.