What Is Breast Cancer?

Cancer begins when cells in a part of the body start to grow out of control. Instead of dying, cancer cells continue to grow and form new, abnormal cells, possibly invading other tissues. The term "breast cancer" refers to a malignant tumor that has developed from cells in the breast.

The breast is made up of 15–20 sections called lobes, consisting of smaller sections called lobules, the milk-producing glands. All are connected by tiny tubes, called ducts, which drain the milk from the lobules to the nipple. The most common type of invasive breast cancer is ductal carcinoma, which begins in the cells of the ducts. Cancer that begins in the lobes or lobules is called lobular carcinoma.

Treatment depends on the stage of the cancer, which is determined by the extent of the cancer in the body. It is based on whether the cancer is invasive or non-invasive, the size of the tumor, how many lymph nodes are involved, and if it has spread to other parts of the body. The stage of a cancer is one of the most important factors in determining prognosis and treatment options.

The earliest form of breast cancer is called carcinoma in situ. The most common type of this non-invasive breast cancer is called ductal carcinoma in situ (DCIS), in which cancer cells have not spread through the walls of the ducts into the surrounding breast tissue. In lobular carcinoma in situ (LCIS), abnormal cells grow within the lobules, or milk-producing glands, but they do not penetrate through the wall of these lobules. In these cases, the cancer has not spread to lymph nodes or distant sites.

Cancer that remains within the original organ are called localized, while tumors that have spread to nearby areas are called regional. Cancer cells that spread to other parts of the body are called metastatic cancer.

Breast cancer occurs in both men and women, although male breast cancer is rare. Breast cancer is the most common cancer in women, except for non-melanoma skin cancers. According to the American Cancer Society, an estimated 226,870 new cases of invasive breast cancers are expected to occur among women in the U.S. during 2012; about 2,190 new cases are expected in men.¹


Early breast cancer usually doesn't cause symptoms. But as the tumor grows, it can change how the breast looks or feels. The common changes include:

You should see your health care provider about any symptom that does not go away. Most often these symptoms are not due to cancer. If you have any of these symptoms, you should tell your health care provider so they may be properly evaluated.

What Are the Risk Factors of Breast Cancer?

Women with certain risk factors are more likely than others to develop breast cancer. A risk factor is something that may increase the chance of getting a disease.

Some risk factors (such as drinking alcohol) can be avoided. But most risk factors (such as having a family history of breast cancer) can't be avoided.

Studies have found the following risk factors for breast cancer:

Having a risk factor does not mean that a woman will get breast cancer. Most women who have risk factors do not develop breast cancer.

Types of Surgical Treatment for Breast Cancer

Treatment options include mastectomy or breast conservation therapy (BCT). Mastectomy is an operation to remove the entire breast, including the nipple and glands (lymph nodes) under the arms called axillary nodes. Mastectomy usually requires a hospital stay. Women who undergo a mastectomy have the option of breast reconstruction.

Breast conservation surgery removes the breast tumor and a margin of surrounding normal tissues. It is also known by other names: lumpectomy, partial mastectomy, segmental mastectomy and quadrantectomy. Breast conserving surgery plus irradiation has been shown to have equivalent outcomes to mastectomy.³ In addition to the breast tumor removal, lymph nodes in the corresponding arm pit need to be checked for involvement of cancer cells. This can be done by a sentinel lymph node biopsy.

Sentinel Lymph Node Biopsy

Sentinel lymph node biopsy is the removal of the sentinel lymph node during surgery. The sentinel lymph node is the first lymph node to receive lymphatic drainage from a tumor. The cancer is likely to spread to the first lymph node from the tumor. A radioactive substance and/or blue dye is injected near the tumor. The substance or dye flows through the lymph ducts to the lymph nodes. The first lymph node to receive the substance or dye is removed. A pathologist views the tissue under a microscope to look for cancer cells. If cancer cells are not found, it may not be necessary to remove more lymph nodes.

The choice between breast-sparing surgery (followed by radiation therapy) and mastectomy depends on many factors:

Why Radiation Therapy?

Radiation therapy follows breast conserving therapy to eliminate any microscopic cancer cells in the remaining breast tissue. Breast-conservation therapy has been shown in studies to have equivalent survival rates to mastectomy in early stage breast cancer patients.² ³  It also provides excellent cosmetic results, leaving the breast intake in appearance and texture while sparing the nipples. Your physician will explain to you if you are an appropriate candidate for breast-sparing surgery.

Radiation Therapy Options:


1. American Cancer Society, Cancer Facts & Figures 2009.

2. Veronesi U, et al. Twenty-year follow-up of a randomized study comparing breast-conserving surgery with radical mastectomy for early breast cancer. N Engl J Med, Vol 347, No 16, 2002:1227-1232.

3. Fisher B, et al. Twenty-year follow-up of a randomized trial comparing total mastectomy, lumpectomy, and lumpectomy plus irradiation for the treatment of invasive breast cancer. N Engl J Med, Vol. 347, No 16;1223-1241.

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See our patient brochure for the advantages of IORT for early stage breast cancer and additional important information on IORT.

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