What is Breast Cancer?

Breast cancer is a disease in which malignant (cancer) cells form in the tissues of the breast. It is considered a heterogeneous disease—differing by individual, age group, and even the kinds of cells within the tumors themselves. Obviously no woman wants to receive this diagnosis, but hearing the words “breast cancer” doesn’t always mean an end. It can be the beginning of learning how to fight, getting the facts, and finding hope.

Women in the United States get breast cancer more than any other type of cancer except for skin cancer. It is second only to lung cancer as a cause of cancer death in women.

Each year it is estimated that nearly 200,000 women will be diagnosed with breast cancer and more than 40,000 will die. Approximately 1,700 men will also be diagnosed with breast cancer and 450 will die each year. The evaluation of men with breast masses is similar to that in women, including mammography.

Check a Breast Cancer Symptom

Learn how to actively maintain and monitor your breast health. Understand the signs and symptoms of breast cancer. Use tools to help decide if it’s time to call the doctor. Take a symptoms quiz (website link) to review what you've learned -- or to assess what you should know about breast cancer symptoms.

Start Here:

Breast Cancer Symptoms

• From breast lumps to nipple retraction, read about the signs and symptoms of breast cancer.
• Breast Lump Image Gallery: Is This Normal?

  What does a "normal" breast look like? Should you be concerned about an abnormal breast lump? What does it look like? Review what signs to look for and when a trip to the doctor is in order.
• Breast Lump FAQs

  A breast lump that feels different than usual may be a cue to call the doctor. Learn more about breast lumps and when to seek professional help.

What If It's Not a Breast Lump?: Illustrated Symptom FAQs

October is Breast Cancer Awareness Month!! 

Breast cancer information

It’s helpful to understand metastatic breast cancer within the context of earlier stages of the disease and other treatments you’ve taken. Here you can review the various breast cancer stages and the distinctions among the kinds of breast cancer recurrence.  You can also learn about the role of hormones in some breast cancers and the available treatment options for women with advanced disease.

A breast is made up of lobules, ducts, fatty tissue, blood vessels, lymph vessels, muscles, and nerves. The lobules are tiny sacs that make milk during breast feeding. There are about one million lobules in each breast. The ducts are tubes that carry the milk from the lobules to the nipple. The fatty tissue surrounds the lobules and ducts to provide support. Lymph vessels carry lymph to lymph nodes in the underarm, above the collarbone, and in the chest. There are also lymph nodes throughout the body.

Your doctor will look at a number of factors, including the size of the tumor, the role of lymph nodes, and how far the cancer has spread, to determine the stage of your breast cancer. There are early stages of breast cancer (0, I, II, and IIIA) and advanced stages (IIIB/C and IV).

Breast Cancer Stages

Early stages of breast cancer

Stage 0

Cancer cells are present in either the lining of a breast lobule or a duct, but they have not spread to the surrounding fatty tissue. This stage is also called ductal carcinoma in situ, or DCIS.

Stage I

Cancer has spread from the lobules or ducts to nearby tissue in the breast. At this stage and beyond, breast cancer is considered to be invasive. The tumor is 2 cm or less in diameter (approximately 1 inch or less); the cancer has not spread to the lymph nodes.

Stage II

In this stage, the tumor can range from 2 cm to less than 5 cm in diameter (approximately 1 to 2 inches); sometimes cancer may have spread to the lymph nodes.

Stage IIIA

In this stage, the tumor is 5 cm or greater in diameter (approximately 2 inches or greater); or the tumor may be of any size where cancer cells have grown extensively into the axillary (underarm) lymph nodes.

Advanced stages of breast cancer

Stage IIIB/C

Known as locally advanced cancer; tumor may be of any size but has spread into the skin of the breast or tissues of the chest wall.

Stage IV

Known as metastatic; cancer has spread from the breast to other parts of the body, such as the bones, liver, lungs, or brain.

Breast cancer recurrence — the return of cancer following primary (initial) treatment — can occur at the same site as the original tumor or somewhere else in the body.

Impact of hormones on breast cancer

Hormones are produced by organs or cells in your body. Hormones, such as estrogen, affect bodily processes. Normal breast cells have receptors for estrogen and progesterone. Some, but not all, breast cancer tumors also have these receptors and need these hormones to grow. Such tumors are called estrogen and/or progesterone receptor positive, or hormone receptor positive. Breast cancer tumors are estrogen and/or progesterone receptor positive in approximately 60% of postmenopausal women. Lab tests of your cancer biopsy give your medical team this information. Receptors are very small parts of a cell. If estrogen is present, it will attach to an estrogen receptor and may make the tumor grow larger.

Estrogen does not cause breast cancer, though it may promote the growth of tumors. Here's how certain breast cancer cells live and grow with the help of estrogen:

Estrogen finds a specialized receiver in a cell, called a receptor.

Estrogen attaches itself to estrogen receptors. These receptors take the estrogen and bring it into the center of the cancer cell (nucleus) so that estrogen can give the signal for the tumor to grow.

Result: cancer cells grow and divide to form more cells.