Ductal Carcinoma in Situ (DCIS)
DCIS stands for ductal carcinoma in situ. When you have this condition, the cells lining the milk ducts (the channels in the breast that carry milk to the nipple) are cancerous, but stay contained within the ducts without growing through into the surrounding breast tissue. DCIS may affect just one area of the breast, but can be more widespread and affect different areas at the same time. Sometimes, DCIS may be described as pre-cancerous, pre-invasive, non-invasive, or intraductal cancer. If DCIS is left untreated, it may, over a period of years, spread into (invade) the breast tissue surrounding the ducts. It is then known as invasive breast cancer. It is important to remember that although DCIS should be treated to prevent it developing into an invasive breast cancer, it is not harmful at this stage. Not every woman with DCIS will go on to develop breast cancer if it is left untreated, but it isn't possible to predict when DCIS will develop into breast cancer. There are three grades of DCIS: low, intermediate, and high. The grade relates to how the cells look under the microscope, and gives an idea of how quickly the cells may develop into an invasive cancer (or how likely it is that the DCIS will come back after surgery). Low-grade DCIS has the lowest risk of developing into an invasive cancer, and high-grade carries the greatest risk.
Causes of DCIS
The exact causes of DCIS are unknown, but certain women appear to be at a higher risk of developing it. This includes women who have never had any children, or who had them late in life, women who started their periods at a young age, or who had a late menopause, and women who have a strong family history of breast cancer. The risk factors involved in developing DCIS are similar to those of developing invasive breast cancer.
Signs and symptoms
DCIS usually shows up on a mammogram as an area where tiny specks of calcium have collected in the breast ducts (known as microcalcification). It is important to remember that most microcalcification is not DCIS or cancer.
A small number of women with DCIS may have symptoms, such as a breast lump or fluid (discharge) coming out of the nipple.
After the mammogram
If an abnormal area is found on the mammogram, the doctor obtains a sample of cells (biopsy) from this area, so that they can be examined under a microscope. The biopsy is carried out using a special needle called a core biopsy needle. A local anaesthetic will be given to numb the area before the biopsy is taken. Alternatively, a fine needle aspiration cytology (FNAC) may be used. This test uses a fine needle and a syringe to draw out some of the cells.
If there is no obvious lump, mammograms can also be used to ensure that the sample of cells is taken from the correct area. Alternatively, the radiologist may insert a wire into the area of abnormal cells, to guide the surgeon to the correct piece of tissue for the biopsy. This is called wire localisation biopsy. A local anaesthetic is given to numb the area before this procedure is carried out.
The treatment for DCIS depends on its extent (how much of the breast it is affecting) and its grading.
The most important part of treatment is the surgical removal of the affected breast tissue, together with an area (margin) of normal breast tissue around it, to ensure that all affected tissue is reomved. This operation is called a wide local excison (WLE).
Wide local excision is an example of breast-conserving therapy (only the area of DCIS is removed, rather than the whole breast).
If the area of DCIS is large, and especially if it is large and high-grade, removal of the breast (mastectomy) may be recommended. Mastectomy is also advised as treatment if the DCIS is affecting more than one area of the breast. This cures the condition in virtually all women and often no further treatment is necessary, although it is important for the other breast to be checked at least yearly by mammogram.
DCIS does not generally spread to the lymph nodes in the armpit (axilla), but sometimes, if the area of DCIS is large or widespread, the lymph nodes may be removed during the surgery and checked for cancer cells. This is because, for some women, there may be an area of invasive cancer cells within the DCIS which could spread into the lymph nodes. Before your operation, your doctor will discuss with you whether it is necessary to remove any of your lymph nodes.
Radiotherapy uses high-energy x-rays to destroy the abnormal cells, while doing as little harm as possible to normal cells. After a wide local excision, radiotherapy is sometimes used to treat the remaining breast tissue. It is most commonly used if the area of DCIS was high-grade. Radiotherapy is normally given every weekday, for 3–6 weeks.
Sometimes, the cancer cells within the area of DCIS have estrogen receptors on their surface. This is known as estrogen-receptor-positive DCIS. This means that the cells rely on the hormone, estrogen, to grow. Estrogen is a female hormone that is naturally produced in the body and it can stimulate some breast cancer cells to divide and grow. If you have estrogen-receptor positive DCIS, you may be prescribed a drug called tamoxifen that is designed to counteract the effects of estrogen.
Tamoxifen works by attaching itself to the estrogen receptors on the surface of the cancer cells. This prevents estrogen from entering the cells and can stop the cells from growing or dividing.
If your DCIS is estrogen-receptor-positive and you have had a wide local excision, you may be given tamoxifen to reduce the risk of developing an invasive breast cancer. However, doctors are unsure of exactly how helpful tamoxifen is to this group of women. Research suggests that women who have not had radiotherapy after a wide local excision will get more benefit from taking tamoxifen than those who have had radiotherapy. Your doctor can discuss how useful tamoxifen will be to you.
After breast-conserving surgery, there is a small risk of DCIS coming back. If you have breast-conservation therapy, you will be offered yearly follow-up appointments, so that if the DCIS comes back it is detected as early as possible. If you notice any change in the breast between these appointments, you can arrange to see the breast cancer specialist earlier. If the DCIS does come back, mastectomy is likely to be the chosen treatment. Breast reconstruction can be done at the same time.
If you have had DCIS, it is important to have your unaffected breast checked regularly by mammogram (at least every three years).
Research into treatments for DCIS is ongoing, and advances are constantly being made. Cancer doctors use clinical trials to assess new treatments. Before any trial is allowed to take place, an ethics committee must have approved it, and agreed that the trial is in the interest of patients.
You may be asked to take part in a clinical trial. Your doctor must discuss the treatment with you so that you have a full understanding of the trial, and what it involves. You may decide not to take part or withdraw from a trial at any stage. You will then receive the best standard treatment available.
This section has been compiled using information from a number of reliable sources, including:
•Oxford Textbook of Oncology (2nd edition). Eds Souhami et al. Oxford University Press, 2002
•Ductal Carcinoma in Situ of the Breast (2nd edition). Silverstein, Lippincott Williams and Wilkins, 2002
•Cancer and Its Management (4th edition). Souhami and Tobias. Oxford Blackwell Scientific Publications, 2003
•Improving Outcomes In Breast Cancer – The Research Evidence. National Institute of Clinical Excellence, 2002.