Ductal carcinoma in situ (DCIS) of the breast is an early, localized cluster of cancer cells that start in the milk passage ducts of the breast but have not penetrated the duct walls into the surrounding tissue. The term "in situ" refers to a tumor that has not spread beyond the place where it originally developed.
Ductal carcinoma in situ of the breast is sometimes described as "pre-cancerous", "pre-invasive", "non-invasive", or "intraductal carcinoma". If left untreated, however, DCIS may progress to ‘true’ breast cancer by spreading into and invading the surrounding healthy breast tissue. Because doctors cannot predict with any degree of certainty whether DCIS will develop into invasive breast cancer, early diagnosis and treatment is crucial. With appropriate treatment, the prognosis (outlook) for women with ductal carcinoma in situ of the breast is excellent.
Fortunately, ductal carcinoma in situ of the breast can often be detected on screening mammography before any symptoms develop. DCIS usually appears on mammography as an area of microcalcification (groups of small calcifications of tissue clustered together within the breast).
Approximately 50,000 new cases of ductal carcinoma in situ of the breast are diagnosed in the United States each year. DCIS represents 10-15% of all new breast cancers diagnosed in the United States and accounts for 30-50% of cancers detected by screening mammography in women less than age 50 years and 15-25% in women over age 50. It also comprises approximately 7-10% of all breast biopsies.
In the past, women with ductal carcinoma in situ of the breast had a mass large enough to be palpated (felt) or nipple discharge before the diagnosis could be made. Since screening mammography became more widely available in the 1980s, however, many cases of DCIS are discovered before any symptoms develop and the average size of DCIS has been signifcantly reduced at the time of discovery.
When an abnormal area has been detected by mammography and ductal carcinoma in situ of the breast is suspected, the diagnosis must be confirmed by removing a sample from the suspicious area of the breast and examining the specimen under a microscope. This procedure is known as a diagnostic biopsy.
The primary goals of treatment of ductal carcinoma in situ of the breast are prevention of local recurrence and prevention of invasive breast cancer.
The surgical treatment options for women with DCIS include:
- Simple mastectomy – surgical removal of a breast, including the nipple and areola, while leaving the underlying muscles and lymph nodes intact.
- Breast-conserving surgery – the tumor is surgically removed while leaving the remaining breast tissues, nipple, and areola intact. This procedure is sometimes also called a lumpectomy.
Because women who undergo breast-conserving surgery for ductal carcinoma in situ of the breast are at risk for recurrence of a tumor either in the same or contralateral breast, radiation therapy may be used to treat the remaining breast tissue. A drug called tamoxifen may be used to as adjuvant therapy in women with estrogen receptor positive DCIS who have undergone breast-conserving surgery and radiation therapy.
