What's the deal with DCIS?

There’s a fair bit of confusion surrounding DCIS (ductal carcinoma in situ). Is it really breast cancer? What does ‘pre-invasive’ mean? How can a cancer be classified as ‘Stage 0’?

Put simply, DCIS is when cancer cells are in a breast duct, but they haven’t mutated enough to spread outside of the duct and into the breast tissue. This is what is meant by ‘pre-invasive’, as the cancer is contained within the duct. This also makes DCIS the earliest form of breast cancer, which is why it’s classed as ‘Stage 0’. The good news is that it is completely curable, and those with DCIS usually have a very good prognosis.

Since DCIS is a very early stage of breast cancer, you can’t feel it as a lump. Instead, it’s usually found as part of a routine mammogram (another reason to book an appointment!). Once DCIS is diagnosed, it is graded to see how aggressive it is, and this can range from slow-growing cells (low grade) to cells that are growing rapidly and that look very different to normal cells (high grade).

DCIS patients will almost always have surgery – either a lumpectomy or a mastectomy, depending on how much of the breast is affected – as part of treatment. For those who have a lumpectomy (also known as breast-conserving surgery or a partial mastectomy) radiation therapy may also be recommended. This treatment is used to get rid of any pre-cancerous cells that remain in the breast after surgery, and it can help to reduce the risk of recurrence. Since DCIS is contained within the duct, you won’t need chemotherapy.

It can be hard to get your head around the idea that while DCIS is a very early form of breast cancer, you may have to have a mastectomy to treat it. It’s important to remember that DCIS is no less important than any other type of breast cancer. It’s normal to feel worried about treatment, or to feel like you’re on an emotional rollercoaster. If you feel like talking to someone outside your family or friends, we fund free counselling sessions or you can join our DCIS community on mybc.

You may also be wondering why you need surgery if it’s not likely to spread into the breast. We don’t know if DCIS will go on to develop into invasive breast cancer, or how quickly this may happen. We also don’t know which patients are more at risk of this happening. This is why it’s common practice to surgically remove DCIS to prevent it becoming invasive, and why a biopsy is taken of DCIS tissue once it’s removed. Around 30% of patients will have invasive cells present in their biopsy. This means that it’s no longer classified as DCIS, and patients will be treated as if they have invasive breast cancer, which may mean having chemotherapy.

You can find out more on DCIS, by watching our webinar, ‘Dealing with DCIS’.