Ductal Carcinoma in Situ (DCIS)

Ductal carcinoma in situ (DCIS) is a type of very early breast cancer where cancer cells line your milk ducts within one or both breasts. Milk ducts are tubes that carry milk from the lobes of your breasts to your nipples so you can breastfeed (chestfeed). The cancer is “in situ,” or situated (contained) inside of your milk ducts.

Healthcare providers may call DCIS noninvasive or pre-invasive breast cancer. This means that the cancer cells haven’t spread beyond the walls of your milk ducts. Ductal carcinoma in situ doesn’t typically metastasize, or spread to other organs in your body, as aggressive or invasive cancers do.

While DCIS can’t spread outside of your breast, it can turn into invasive ductal carcinoma — which can spread outside of your breast — in some cases. That’s why talking to a healthcare provider is so important. They can discuss treatment options to help reduce this risk.

How common is DCIS?

Ductal carcinoma in situ is a common form of breast cancer among women and people assigned female at birth (AFAB), accounting for 20% to 25% of new breast cancer diagnoses each year. Men and people assigned male at birth (AMAB) can get DCIS, but it’s rare (less than 0.1% of cancer diagnoses).

DCIS cases are on the rise. But experts believe this is because more people are being diagnosed and treated, not because more people are getting DCIS.