The short answer
Ductal carcinoma in situ, or DCIS, means abnormal cells are found in the lining of a breast duct. NCI says they have not spread outside the duct. In some cases DCIS may become invasive, and NCI says it cannot yet tell which cases will. This page explains the term and what to ask your care team.
NCI describes DCIS as abnormal cells in the lining of a breast duct that have not spread outside the duct.
NCI says DCIS may progress to invasive breast cancer in some cases.
NCI says it cannot yet tell which cases could become invasive.
Ask your care team what your report shows and what options fit you.
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This page is for anyone whose breast biopsy or surgery report says "ductal carcinoma in situ" or "DCIS." It explains the term and what to ask your care team.
What DCIS means
NCI describes DCIS as abnormal cells found in the lining of a breast duct. The ducts are the tubes that carry milk to the nipple (MedlinePlus). NCI says the cells have not spread outside the duct into nearby breast tissue.
"In situ" means "in place." The cells have stayed where they started.
Why it still needs a plan
NCI says DCIS may progress to invasive breast cancer in some cases. NCI also says it cannot yet tell which cases will.
That uncertainty is why your care team will talk with you about options. What is right depends on your whole report and your situation.
DCIS versus invasive ductal carcinoma
The names are similar. Invasive ductal carcinoma means cancer cells have spread outside the duct into nearby breast tissue. DCIS means they have not. Some reports list both. Ask your care team which one your report shows.
Ask these before you leave
- Does my report show DCIS only, or invasive cancer too?
- What were the margins?
- What are my options, and what are the trade-offs?
Related pages
See What Does Carcinoma In Situ Mean? and What Is Invasive Ductal Carcinoma?.
Sources
Common questions
What is DCIS?
NCI describes it as abnormal cells in the lining of a breast duct that have not spread outside the duct into nearby breast tissue.
Is DCIS invasive cancer?
No. NCI says the abnormal cells have not spread outside the duct. NCI notes DCIS may become invasive in some cases.
Does DCIS always become invasive?
No. NCI says DCIS may progress to invasive breast cancer, but it cannot yet tell which cases will.
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Sources last checked: 2026-10-02 what this meansLast updated: 2026-10-02Next planned review: 2027-09-27
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Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and then compared with the sources listed on it, looking for statements those sources do not back up. That check is not a sentence-by-sentence record and can miss errors. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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