Ductal carcinoma in situ
Ductal carcinoma in situ (DCIS) is a noninvasive breast cancer limited to the milk ducts within the breast and is diagnosable with mammography. The potential for DCIS to become an invasive cancer (i.e., spreading of the cancer beyond the confines of the milk duct) can be managed via chemotherapy, surgery, and radiation. Diagnosis and treatment of DCIS can allow the breasts to remain intact in many cases.
Definition & Facts
About 12,000 women will be diagnosed with DCIS in the U.S. this year. Individuals whose close relatives have had cancers of the breast, colon, ovary, or uterus or who have BRCA1 and BRCA2 defects are at greater risk. Early menstruation or late menopause, alcohol abuse, birthing of a first child after age 30, estrogen therapy for extended periods, obesity, and radiation exposure are also associated with increased incidence of DCIS.
DCIS recurs after five or ten years in less than one third of women treated with a DCIS managed with lumpectomy (a form of breast-conserving surgery). When radiation is combined with surgery, recurrence risk is halved. Cancer may manifest as noninvasive DCIS in half of the cases of recurrence, but it may manifest as an invasive cancer in the other half.
Incidence of DCIS is increasing due to women living longer, since DCIS risk increases with age. Incidence may also be increasing due to increased screening mammography of women and to better mammography resolution of potential lesion sites. Technically, these data may not argue for increased incidence of DCIS, but for increased efficiency in identification.
Symptoms & Complaints
Cancer, on the most elemental level, is development of abnormal cells, uncontrolled by normal cell constraints, proliferating without check. Unlike benign abnormal cells with focused growth that is self-contained (e.g., a wart), malignant cancerous cells are not contained within any margin or boundary (a cancerous tumor) and escape into the normal tissues of the body. Ductal carcinoma in situ is often referred to as precancerous because the cancer cells haven't yet spread beyond the milk ducts, but they can become invasive over time.
In the case of DCIS, no specific cause for development of malignant cells has been identified. Red flags for suspicion of DCIS development suggest that genetic mutations (especially in the BRCA1 and BRCA2 genes) increase risk of DCIS but do not automatically cause the cancer. (Only 10% of all breast cancers occur in these gene-families).
Faulty gene controls in any one individual are “turned off and on” by a process yet to be understood. Risk factors have been suggested: chemicals in the diet or the environment (e.g. tobacco, pollutants, insecticides, etc.), malnutrition or obesity, sedentary lifestyle, radiation exposure (UV light from the sun, gamma and X-rays, radon, etc), exposure to known carcinogens (arsenic, asbestos, benzene, formaldehyde, lead, and certain cosmetics and dyes).
Diagnosis & Tests
Any diagnostic evaluation begins with a physical examination of the breast and adjacent lymph nodes. Abnormal or suspicious findings in that evaluation necessitate further tests. If breast evaluation reveals breast structures that are abnormal for a patient’s age and sex, the clinician will seek a better look at the breast.
A biopsy of the breast may sample the lump to determine what type of cell is responsible (e.g. malignant tumor versus benign breast cyst). Biopsies may be taken with a needle that extracts a small amount of cells or through surgical removal of a larger area of suspicious tissue. Blood tests will be taken as well to test the abnormal cells for whether or not they contain proteins that are receptive to certain hormones which in turn fuel their growth. This can affect options for treatment later on when such cancers that are receptive to hormones can be treated with drugs that inhibit those hormones and thereby reduce cancer growth.
Imaging technology may define the extent and margins of the lump (a palpable tumor typically extends beyond the edges of the lump felt within the breast). Imaging may employ ultrasound (sonography), conventional X-ray, computerized tomography (CT scan), magnetic imaging (MRI), or even positron emission tomography (PET scan). The choice of scan will be determined by the clinician’s sense of where a tumor may have penetrated beyond its initial boundaries.
Treatment & Therapy
The patient’s physician will discuss results and will jointly with the patient determine a treatment plan; e.g. radiation, chemotherapy, surgery, or a combination of therapies. The size and location of a breast lump will suggest a specific strategy. In the case of a larger tumor, the initial management may be to shrink the malignant mass using radiation or chemotherapy. Once reduced in size, removal of the tumor will cause less tissue damage to adjacent tissues. Mastectomy may be opted for under certain circumstances such as family history, a large tumor size and genomic tests that reveal an increased risk of recurrence.
If the cancer is revealed to be hormone-receptor-positive, treatment may include the administering of drugs that prevent certain hormones from encouraging cancer growth. Tamoxifen is one such drug that is commonly used to treat ductal carcinoma in situ, and it helps reduce the risk of recurrence.
Prevention & Prophylaxis