Breast cancer is a common malignancy, with almost 200,000 new cases diagnosed in the United States each year. The disease occurs most frequently in women and rarely, in men. The breasts are glands that produce and release milk in women in association with pregnancy. Breast cancer develops from cells in the breast.

The normal breast has 6 to 9 overlapping sections called lobes and within each lobe are several smaller lobules that contain the cells that produce milk. The lobes and lobules are linked by thin tubes called ducts, which lead to the nipple in the center of the breast. The spaces around the lobules and ducts are filled with fat. Lymph vessels carry colorless fluid called lymph, which contains important immune cells. The lymph vessels lead to small bean-shaped structures called lymph nodes. Clusters of lymph nodes are found in the axilla (under the arm), above the collarbone and in the chest.

The suspicion of breast cancer first arises when a lump is detected in the breast during breast examination or a suspicious area is identified during screening mammography. In order to diagnose the cause of the suspicious area or lump in the breast, a physician will perform a biopsy. A biopsy can be performed on an outpatient basis. During a biopsy, a physician removes cells for examination in the laboratory to determine whether cancer is present. Other information obtained from the biopsy sample will play an important role in treatment decisions. If the biopsy indicates that cancer is present, additional surgery may be performed after the patient and doctor select a course of treatment.

There are many types of breast tumors. Some breast tumors are benign (not cancerous). Benign breast tumors such as fibroadenomas or papillomas do not spread outside of the breast and are not life threatening. Other breast tumors are malignant (cancerous). The most common type of breast cancer is called ductal carcinoma and begins in the lining of the ducts. Another type of cancer is called lobular carcinoma, which arises in the lobules. When cancer is identified in the biopsy specimen, several other tests are performed on the specimen in order to further classify the cancer and determine the optimal treatment strategy. These additional laboratory tests should include:

1) Identification of the presence of estrogen and progesterone receptors : These receptors have prognostic significance and can affect treatment decisions.

2) Approximately 30% of breast cancers overexpress a protein called Her 2-neu . This protein is involved in regulating cellular growth and may be found on the surface of normal cells. However, overexpression of Her2-neu is associated with a poorer prognosis. Laboratory tests can determine Her2-neu overexpression at a genetic or a protein level. Her2-neu is also a target for a monoclonal antibody called Herceptin® and therefore, should be accurately measured on all breast cancers.

3) The proliferative index or S-phase measures how fast the breast cancer cells are growing. High values, indicative of faster growing cells, tend to indicate a poorer outcome following treatment than low values.

While many other laboratory tests are being evaluated to help patients determine their prognosis, other tests do not currently add independent prognostic value for patients.

Optimal treatment of breast cancer often requires several different treatment modalities, including surgery, radiation, chemotherapy and hormonal therapy. Following a biopsy-proven diagnosis of breast cancer, additional evaluation is necessary to determine if the cancer has spread elsewhere in the body. Breast cancers may spread to adjacent skin, local or regional lymph nodes, or through the blood to other locations in the body, such as the liver, bones and lungs. In order to effectively plan treatment, it is important to first determine the extent of the spread or the stage of the cancer. Determining the stage of the cancer requires a number of procedures, which may include blood tests, chest x-rays, mammography, and occasionally Computerized Tomography/Magnetic Resonance Imaging (CT/MRI) or bone scans.

For over 30 years, the standard of practice for breast cancer staging has included an axillary lymph node dissection. During this procedure, a surgeon removes lymph nodes under the arm to aid in determining the spread of cancer in the body. If cancer spreads from its site of origin, it commonly spreads first to the lymph nodes that initially collect the excess lymph fluid from that area (sentinel lymph nodes). With current standard staging procedures, axillary lymph nodes are removed during surgery and are tested to determine if they contain cancer cells that may have spread from the breast. The presence or absence of cancer cells in axillary lymph nodes is an essential factor in defining optimal treatment strategies following surgery. Women who have cancer cells present in their axillary lymph nodes are at a higher risk for a cancer recurrence, so they are treated more aggressively following surgery than women who have no cancer cells detected in their axillary lymph nodes.

During an axillary lymph node dissection, 20-40 lymph nodes may be removed. Unfortunately, this procedure may be associated with chronic side effects including pain, infection, limited shoulder motion, numbness and lymphedema (swelling of the arm due to an accumulation of lymph fluid). Since these complications can become debilitating, a new strategy is currently being evaluated and refined in clinical trials. This strategy incorporates the removal of only the sentinel lymph node(s) to determine the extent of cancer spread. Because the sentinel lymph node(s) (SLN) receives initial drainage from the cancer, it has the highest probability of containing cancer cells if the cancer actually has spread. Therefore, other axillary lymph nodes may be spared from unnecessary removal if no cancer cells are present in the SLN. This practice virtually eliminates the development of complications associated with standard axillary node dissection.