Ductal Carcinoma in Situ (DCIS)

What is ductal carcinoma in situ (DCIS)?

DCIS stands for ductal carcinoma in situ. This means the cancer cells are inside the milk ducts or ‘in situ’ (in place) and have not developed the ability to spread either within or outside the breast. DCIS is an early form of breast cancer and may be described as a pre-invasive, non-invasive or intraductal cancer. It may affect just one area of the breast, but can be more widespread and affect different areas at the same time.

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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. DCIS is not harmful in itself, but it is usually treated to prevent it developing into an invasive breast cancer. Not every woman with DCIS will go on to develop breast cancer if it is left untreated, but it is not possible to predict reliably which women with DCIS will go on to develop invasive breast cancer. Doctors haven’t yet reached a consensus about the nature of this disease and its management, although research is underway to inform this such as the LORIS trial - a trial comparing sugery with active monitoring for low risk DCIS (see Cancer Research UK for more information).

Treatment, usually surgical removal of the affected area(s) of the breast, aims to prevent the development of invasive cancer. For most women this will mean removing only a small part of the breast (lumpectomy or wide local excision). However, about four out of ten women (40%) diagnosed with DCIS in the UK have their whole breast removed (mastectomy) because more than one part of the breast is affected (Thornton H, Edwards A, Baum M. Women need better information about routine mammography. BMJ 2003;327'101-3).

More information about wide local excision and mastectomy can be found on Macmillan Cancer Support's website.

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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.
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Most women with DCIS have no signs or symptoms and only know they have it when it is seen on a mammogram. This is why DCIS has been diagnosed more frequently since three-yearly breast screening for women aged 50-70 was introduced by the UK National Health Service (NHS). The NHS Breast Screening Programme is being gradually extended in England to women aged 47 to 49, as well as to those aged 71 to 73 as part of a Trial.

DCIS usually shows up on a mammogram as an area where tiny specks of calcium have collected in the breast ducts, known as micro-calcification. It is important to remember that most micro-calcification is not DCIS or cancer. A few women with DCIS, however, do have symptoms, such as a breast lump, fluid (discharge) coming out of the nipple, or a type of rash involving the nipple called Paget’s disease (see Diagnostic mammograms).

In the UK, non-invasive cancers such as DCIS about 3 in every 200 women screened, this adds up to about 4,000 women each year in the UK (NHS Breast screening programme July 2016). Only one of the women we spoke with had ever heard of DCIS before her own diagnosis. Many were unsure as to whether it was actually cancerous or not. Most wanted more information about DCIS and felt unprepared for the diagnosis because they’d had no symptoms. With hindsight, a few women wondered if they had actually had a symptom but one which hadn’t been noticeable enough for them to visit their GP.

See the 'Resources' section for a list of resources related to DCIS.

Last reviewed July 2017.

Last updated July 2017.

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