DCIS

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DCIS
Updated June 2004
breasthealth.com

What is DCIS?

To understand what DCIS is, it helps to know what your breast looks like on the inside. The breast contains lobules (milk sacs) that produce milk, and ducts that take the milk to the nipple. These are surrounded by fatty tissue. Sometimes the cells on the inside of the milk ducts become abnormal in shape and size, and begin to multiply in an uncontrolled way. See illustration below.

DCIS is the name for abnormal cells that are contained in the milk ducts of the breast. The causes of DCIS are unknown.

A breast showing DCIS and invasive breast cancer



Illustration adapted from www.cancerhelp.org.uk with permission

DCIS is sometimes called ‘non-invasive breast cancer’, a ‘pre-cancer’ or an ‘intraductal cancer’.

What’s the difference between DCIS and invasive breast cancer?
In DCIS, the abnormal cells stay inside the milk ducts and do not spread to other parts of the breast or body. A woman cannot die from having only DCIS.

In invasive breast cancer, the abnormal cells spread outside the ducts into the breast tissue and have the potential to spread to other parts of the body. Although invasive breast cancer can be treated successfully, some women die from the disease when it spreads outside the breast.

© National Breast and Ovarian Cancer Centre 2008