Breast cancer is a type of cancer that starts in the breast. Cancer starts when cells begin to grow out of control. (To learn more about how cancers start and spread, see What Is Cancer?)
Breast cancer cells usually form a tumor that can often be seen on an x-ray or felt as a lump. Breast cancer occurs almost entirely in women, but men can get breast cancer, too.
It’s important to understand that most breast lumps are benign and not cancer (malignant). Non-cancerous breast tumors are abnormal growths, but they do not spread outside of the breast. They are not life threatening, but some types of benign breast lumps can increase a woman's risk of getting breast cancer. Any breast lump or change needs to be checked by a health care professional to determine if it is benign or malignant (cancer) and if it might affect your future cancer risk. See Non-cancerous Breast Conditions to learn more.
Breast cancers can start from different parts of the breast.
Most breast cancers begin in the ducts that carry milk to the nipple (ductal cancers)
Some start in the glands that make breast milk (lobular cancers)
There are also other types of breast cancer that are less common like phyllodes tumor and angiosarcoma
Although many types of breast cancer can cause a lump in the breast, not all do. See Breast Cancer Signs and Symptoms to learn what you should watch for and report to a health care provider. Many breast cancers are also found on screening mammograms, which can detect cancers at an earlier stage, often before they can be felt, and before symptoms develop.
Knowing how your breasts normally look and feel is an important part of breast health. Although having regular screening tests for breast cancer is important, mammograms do not find every breast cancer. This means it's also important for you to be aware of changes in your breasts and to know the signs and symptoms of breast cancer.
The most common symptom of breast cancer is a new lump or mass. A painless, hard mass that has irregular edges is more likely to be cancer, but breast cancers can be tender, soft, or round. They can even be painful. For this reason, it's important to have any new breast mass, lump, or breast change checked by an experienced health care professional.
Other possible symptoms of breast cancer include:
Swelling of all or part of a breast (even if no lump is felt)
Skin dimpling (sometimes looking like an orange peel)
Breast or nipple pain
Nipple retraction (turning inward)
Nipple or breast skin that is red, dry, flaking or thickened
Nipple discharge (other than breast milk)
Swollen lymph nodes (Sometimes a breast cancer can spread to lymph nodes under the arm or around the collar bone and cause a lump or swelling there, even before the original tumor in the breast is large enough to be felt.)
Although any of these symptoms can be caused by things other than breast cancer, if you have them, they should be reported to a health care professional so the cause can be found.