Ductal carcinoma in situ, or DCIS for short, is the earliest form of breast cancer. Although DCIS needs to be treated, it isn’t a life-threatening condition.
Breast cancers usually start in the cells that line the lobes and milk ducts. In DCIS, there are cancer cells lining the ducts but they are completely contained in the ducts. They haven’t started to spread into the surrounding breast tissue. Before cancer cells develop the ability to spread, they are called non-invasive or in situ cancers. DCIS is one of these non-invasive cancers.
As DCIS is a very early form of breast cancer, women are usually diagnosed when they have a mammogram (breast x-ray) as part of the National Breast Screening Programme.