Breast cancer is the most commonly diagnosed cancer among American women and the second leading cause of cancer death (lung cancer is number one). This year, the American Cancer Society estimates 212,920 cases of invasive breast cancer will be diagnosed among women in the U.S. About 41,430 women will die from the disease.

Breast cancers are staged according to their size and how far they have spread. The system ranges from stage 1 (small tumors that have not spread beyond the breast) to stage four (cancer that has spread to other areas of the body).

Cancer begins when, for unknown reasons, an abnormal cell develops and begins to divide. Each time the abnormal cell divides, it produces more abnormal cells, leading to a tumor. Initially, the cancer cells tend to remain in the initial area. Researchers have identified this as stage 0, or carcinoma in situ. Stage 0 breast cancer is considered the earliest form of the cancer, because the abnormal cells have not yet invaded surrounding tissue. (Stage 1 tumors, on the other hand, have grown into surrounding tissue and are considered invasive.)

There are two forms of stage 0 breast cancer. In ductal carcinoma in situ (DCIS) the abnormal cells are found in the lining of the ducts that carry milk to the nipple. The cells can grow to cover a large area, but will not spread outside of the duct. The American Cancer Society estimates 61,980 new cases will be diagnosed in the U.S. this year.

The second form of stage 0 breast cancer is called lobular carcinoma in situ (LCIS). In this condition, the abnormal cells are located in the lobules (areas containing the glands that produce breast milk) and remain confined to the affected lobule. Many physicians don't consider LCIS to be a true breast cancer.

Diagnosing DCIS

Breast surgeon, Nancy Elliott, M.D., says the number of diagnosed cases of DCIS is increasing. At Montclair Breast Center in New Jersey, about 40 percent of newly diagnosed breast cancers are found at stage 0. The rise in cases has been attributed to two factors. First, the risk for breast cancer increases with age. Since women are living longer and the average age of women is increasing, doctors are likely to see more cases. Second, more women are being screened and mammography quality is increasing. Thus, more cancers are being detected at very early stages.

Elliott says when the abnormal cells die, tiny deposits of calcium are left behind. On a mammogram, the areas of dead cells may appear as a cluster of microcalcifications. Not all breast cancers have the calcification. But when these areas are detected on mammograms, doctors will often perform a biopsy (surgical removal of some or of the suspicious area). Examination of the tissue sample under a microscope is needed to confirm the diagnosis.

Treating DCIS

By definition, DCIS is confined to the duct. However, it can sometimes progress into invasive cancer (i.e., spread outside the duct). Research suggests women with DCIS have a 2- to 8-fold risk of developing invasive breast cancer. For an unknown reason, women 20 to 49 have the highest risk of eventually developing stage III or stage IV breast cancer.

There is no clear consensus on how to treat women with DCIS. Recommendations are generally based upon a woman's age, size and spread of the abnormal cells, family history and patient preferences. Most patients will have lumpectomy (breast conserving surgery that removes only the abnormal area and a small area of surrounding tissue). The surgery is usually followed by radiation treatment. If DCIS is in more than one location in the breast, or covers a large area, doctors may recommend a mastectomy.

For general information on stage 0 breast cancer:

American Cancer Society, or contact your local chapter

Breastcancer.org

National Cancer Institute

National Women's Health Information Center

Y-ME National Breast Cancer Organization