Breast cancer is the most common cancer occurring in women (excluding cancers of the skin) and the second most common cause of death from cancer in women, after lung cancer. Men can also develop breast cancer, but male breast canceris rare, accounting for less than 1% of all breast cancer cases. If diagnosed at an early stage, breast cancer has a hopeful cure rate. Up to approximately 97% of women diagnosed with localized breast cancer will be alive five years after their diagnosis.

Note: Estimated new cases and deaths from breast cancer (women only) in the United States in 2004:

New cases: 215,990.

* Deaths: 40,110.

The breast is comprised mainly of fatty tissue. Within this tissue is a network of lobes, which are made up of many tiny lobules that contain milk glands. Tiny ducts connect the glands, lobules, and lobes and carry the milk from the lobes to the nipple, located in the middle of the areola. Blood and lymph vessels run throughout the breast; the blood nourishes the cells, and the lymph drains the waste.

About 90% of all breast cancers occur in the ducts or lobes, with almost 75% of all breast cancers beginning in the cells lining the milk ducts. These cancers are called ductal carcinomas. Cancers that begin in the lobes are called lobular carcinoma and are more likely to be found in both breasts.

If the disease has spread away from its place of origin, it is called invasive or infiltrating ductal or lobular carcinoma. Disease that has not spread is called in situ, meaning "in place." The course of in situ disease, as well as its treatment, varies, depending on its place of origin. Currently, oncologists recommend that ductal carcinoma in situ (DCIS), which accounts for the majority of in situ breast cancers, be surgically removed to prevent progression to invasive disease.

Breast cancers grow at different rates, but some oncologists estimate the average tumor doubles in size every 100 days. Since cancers start with one irregular cell, even with this doubling time, they may not be palpable (able to be felt) for years. Mammography can find tumors that are too small to be felt, but even so, the tumors have probably been growing for years before they are large enough to be visible on a mammogram.

Breast cancer cells migrate to the lymph nodes under the arm (axillary), in the neck (cervical), or those just below the collarbone (supra-clavicular). The most common sites of metastasis, or spread, of breast cancer are skin, distant lymph nodes, bone, lung, and liver.

As we well know, there are many kinds of cancer; unfortunately they all come about because of the out-of-control growth of abnormal cells.