The incidence of breast cancer has been increasing steadily for decades. In 1972 when President Nixon declared our national war on cancer, a woman's lifetime risk of developing breast cancer was 1 in 20. Today breast cancer rates have escalated to the point where women's lifetime risk of developing breast cancer is 1 in 8. In the year 2002, the American Cancer Society estimates that nearly 203,500 women will be diagnosed with breast cancer and approximately 39,600 women will die from the disease. This means that approximately every two and a half minutes a woman in the United States is diagnosed with breast cancer and that approximately every thirteen minutes, a woman dies from this disease. Breast cancer has become the second largest cause of cancer death in women, after skin cancer, and the leading cause of death for women between the ages of 35 and 54.

Malignant Breast Tumors
One of the most common ways to classify breast cancer is according to the type of cells where the cancer originates, such as the lobule, duct or connective tissue. Each breast has 15 to 20 sections called lobes and each contains many smaller sections called lobules. The lobes and lobules are connected by a network of thin tubes called ducts. Ductal cancer is the most common type of breast cancer, accounting for 85 to 90% of the cases.(1) Lobular cancer occurs in 10 to 12% of cases. Inflammatory breast cancer is an uncommon form of the disease, in which the breast becomes warm, red, swollen and inflamed.

Tumor Grade
Each type of breast cancer can be examined for its degree of "differentiation," which classifies the cancer according to how different its cells are from normal cells. This varies from well differentiated to poorly differentiated. Well differentiated cells are very similar to the cells of origin. On the other hand, poorly differentiated cells have bizarre appearances, retaining only a few characteristics of the original normal cells. This description of tumor differentiation is referred to as tumor "grade." Low-grade malignancies are well differentiated, while high-grade indicates poor differentiation. Determination of tumor grade is meaningful because this is highly related to the degree of aggressiveness of the cancers and to patient survival, with high-grade cancers usually carrying the worst prognoses.

Carcinoma In situ
Ductal breast malignancies are divided into two categories, pre-invasive which have not invaded surrounding tissues yet, and invasive. Pre-invasive ductal cancer is called intraductal carcinoma in situ (Latin for "in position"). This is a very early stage of breast cancer, which is so small that it can never be diagnosed on breast examination. Mammography is the only diagnostic method that can detect this in situ stage. In modern mammography centers, ductal carcinoma in situ (DCIS) composes 25% of all breast cancers detected by screening mammography.(2) In DCIS, the ductal cancer cells remain within the ducts, with no sign of outside tissue invasion. If DCIS is not treated surgically, it frequently evolves into invasive ductal carcinoma.(3) It is believed that all invasive ductal cancers began as non-invasive forms.

Lobular carcinoma in situ
Invasive lobular carcinomas only account for about 10% of all breast cancers and they tend to be somewhat less aggressive than invasive ductal carconomas. Unlike invasive ductal carcinomas, it is now believed that lobular carcinoma in situ (LCIS) is not a precursor of invasive lobular carcinoma. The confusion exists because LCIS, while it has the word carcinoma in its name, does not behave like a cancerous condition. It does not grow, form masses, transform into invasive cancer, or metastasize. Therefore, it does not represent a true<