Sylvester Comprehensive Cancer Center

Definition: Breast Cancer

Front view of breast

What is Breast Cancer?

Breast cancer is cancer that forms in the cells of the breasts. To understand breast cancer and how it spreads, it is helpful to understand a little about the anatomy of the breasts.

The female breast is made up mainly of lobules (milk-producing glands), ducts (tiny tubes that carry the milk from the lobules to the nipple), and adipose tissue (fatty tissue) and connective tissue surrounding the ducts and lobules, blood vessels, and lymphatic vessels.

Most breast cancers begin in the cells that line the ducts (ductal carcinoma). Some begin in the cells that line the lobules (lobular carcinoma), while a small number start in other tissues.

When breast cancer spreads, or metastasizes, cancer cells are found in the lymph nodes under the arm. If the cancer reaches these nodes, it means that cancer cells may have spread to other parts of the body through the bloodstream or lymphatic system. When this occurs, the disease is called metastatic breast cancer.

What Are The Different Types of Breast Cancer?

There are several types of breast cancer; the more common types include:

  • Invasive Ductal Carcimona – The most common type of breast cancer is invasive ductal carcinoma, which forms in a milk duct, breaks through the wall of the duct, and grows into the fatty tissue of the breast.
  • Ductal Carcinoma In Situ (DCIS) – Considered the earliest form of breast cancer, DCIS is the presence of abnormal cells inside a milk duct. DCIS is non-invasive, meaning the cancer has not spread beyond the duct. About one in five new breast cancer cases are DCIS, which is often detected with a mammogram. Nearly all women diagnosed at this early stage of breast cancer have a good prognosis.
  • Invasive Lobular Carcinoma – Invasive lobular carcinoma starts in the lobules and accounts for about one in 10 cases of invasive breast cancer.
  • Lobular carcinoma in situ (LCIS) – LCIS begins in the lobules but does not grow beyond and is not considered a cancer, however, women with this condition are at a higher risk for invasive breast cancers.
    Less common types of breast cancer include:
  • Inflammatory Breast Cancer – A rare diagnosis, inflammatory breast cancer accounts for only about 1 to 3 percent of all breast cancer cases. This aggressive form of breast cancer causes different symptoms than other breast cancers and may not produce a noticeable lump or tumor in the breast. Symptoms of inflammatory breast cancer may include: thickening of the skin, redness, irritation, swelling, tenderness, and itching. These changes are not caused by inflammation or infection, but by cancer cells blocking lymph vessels in the skin.
  • Triple-Negative Breast Cancer – Breast cancers (usually invasive ductal carcinomas) whose tumor cells lack estrogen and progesterone receptors and do not have an excess of the HER2 protein on their surfaces are referred to as triple-negative breast cancers. These aggressive cancers are more common in younger women and in African-American women. Triple-negative breast cancers grow and spread faster than most other types of breast cancer and are not responsive to certain treatments, such as hormone therapy.

Breast Cancer in Men

Breast cancer is about 100 times more common among women, but occasionally occurs in men. Breast cancer accounts for less than 1 percent of cancer deaths among men. The American Cancer Society estimates 2,000 new cases of invasive breast cancer are diagnosed annually among men in the U.S.

Many people do not realize men have breast tissue and can develop breast cancer. Men’s breast tissue contains ducts. Like all cells of the body, a man’s breast duct cells can undergo cancerous changes. Although certain risk factors may increase a man’s chances of developing breast cancer, the cause of most breast cancers in men is unknown.

Most of the information about treating male breast cancer comes from doctors’ experience with treating female breast cancer. The prognoses for men with breast cancer are similar to that of women with the disease. There are too few men with breast cancer for doctors to study in clinical trials.