What is ductal carcinoma in situ (DCIS)?

Ductal carcinoma in situ (DCIS) is a non-invasive breast cancer.

With DCIS, the abnormal cells are contained in the milk ducts (canals that carry milk from the lobules to the nipple openings during breastfeeding). It’s called “in situ” (which means “in place”) because the cells have not left the milk ducts to invade nearby breast tissue.

Image source: National Cancer Institute (http://www.cancer.gov)

DCIS is also called intraductal (within the milk ducts) carcinoma. You may hear the terms “pre-invasive” or “pre-cancerous” to describe DCIS.

DCIS is treated to try to prevent the development of invasive breast cancer.

Learn about treatment for DCIS.

DCIS diagnosed with invasive breast cancer

DCIS can be found alone or with invasive breast cancer.

If DCIS is diagnosed with invasive breast cancer, treatment and prognosis are based on the invasive breast cancer (not the DCIS).

Learn about treatment for early breast cancer.

Treatment and prognosis for DCIS

Surgery (with or without radiation therapy) is recommended to treat DCIS. Some women also take hormone therapy (tamoxifen or an aromatase inhibitor).

With treatment, prognosis (chance of survival) is usually excellent.

Learn more about treatment for DCIS.

Why is DCIS treated?

DCIS is non-invasive, but without treatment, the abnormal cells could progress to invasive cancer over time.

Health care providers cannot predict which cases of DCIS will progress to invasive breast cancer and which will not. Because DCIS might progress to invasive breast cancer, almost all cases of DCIS are treated.

Risk of developing invasive breast cancer after DCIS

After treatment for DCIS, there’s a small risk of:

• DCIS recurrence (return of DCIS)
• Invasive breast cancer

These risks are higher with lumpectomy plus radiation therapy than with mastectomy [5].

However, overall survival is the same after either treatment [5].

Higher grade DCIS appears more likely than lower grade DCIS to progress to invasive breast cancer after treatment [6].

With close follow-up, invasive breast cancer is usually caught early and can be treated effectively.

Learn about treatment for DCIS.