Ductal Carcinoma in Situ (DCIS)

April 10, 2025

This page was reviewed under our medical and editorial policy by Susan Yost, Ph.D., staff scientist, Department of Medical Oncology & Therapeutics Research, City of Hope^® Cancer Center Duarte

Ductal carcinoma in situ (DCIS) is the earliest form of breast cancer, sometimes called Stage 0 breast cancer or intraductal carcinoma. It is considered noninvasive, meaning the cancer cells are inside the milk ducts and have not spread to nearby tissue.

DCIS represents about 20% of newly diagnosed breast cancers, making it a relatively common finding. Most women diagnosed with DCIS may be treated successfully, offering a strong chance for recovery at this early stage.

What Is DCIS?

DCIS is an early form of breast cancer in which abnormal cells are found inside the milk ducts but have not spread to nearby breast tissue. Because the cells are contained within the ducts, DCIS is unable to spread to other parts of the body. In some cases, however, DCIS may develop into invasive breast cancer. This means the cancer cells break through the ducts and start affecting surrounding tissues.

This diagnosis may be concerning for patients because there is no way to predict which cases of DCIS might become invasive over time. That is why treatment is recommended for almost all women diagnosed with DCIS, even though it is a noninvasive condition. The goal of treating DCIS is to remove or destroy the abnormal cells before they have a chance to spread.

While the idea of a breast cancer diagnosis may be frightening, it is important to remember that DCIS is highly treatable. By catching these abnormal cells early, patients may have a chance of preventing the disease from progressing.

Is DCIS Cancer?

Ductal carcinoma in situ is considered a form of breast cancer, but it is noninvasive. It starts in the cells lining the ducts of the breast, which is where most breast cancers begin. However, in DCIS, the abnormal cells stay inside the ducts and have not spread into surrounding breast tissue.

While DCIS is technically a cancer, it is often referred to as in situ, meaning it has not invaded deeper tissues or other parts of the body. Once it spreads, it becomes invasive breast cancer.

What Causes DCIS?

The exact cause of ductal carcinoma in situ remains unclear, but certain risk factors may increase the likelihood of developing it. Some individuals with DCIS have a genetic predisposition, particularly those with BRCA1 or BRCA2 gene mutations, which are known to raise the risk for developing breast cancer. However, not all cases of DCIS are linked to these mutations. And oftentimes, the exact cause for DCIS in an individual is not known.

Some factors may increase the chance that DCIS will progress to invasive breast cancer. Higher lifetime exposure to estrogen, whether from natural hormone levels or hormone replacement therapy after menopause, has been associated with an increased risk for developing breast cancer, including DCIS.

Lifestyle choices, such as regular alcohol consumption, also play a role in increasing breast cancer risk. Additionally, individuals with close relatives — such as a mother or sister who has breast cancer — have a higher risk for developing the disease themselves.

Although these factors raise the risk of DCIS, having one or more of them does not mean a person will develop the disease. Each case is unique, and many people with risk factors never develop DCIS.

DCIS Diagnosis and Testing

The diagnostic process for DCIS often begins after a positive screening mammogram. A mammogram usually includes two views of each breast, which helps detect abnormalities, though it does not confirm whether a finding is cancerous.

Further testing is needed if the mammogram shows suspicious findings, such as clusters of tiny calcium deposits (microcalcifications). These calcifications often appear in patterns. When they look irregular or branch-like they may raise suspicion for DCIS.

The care team may perform a diagnostic mammogram for additional views of the area in question to get a clearer picture. This more detailed imaging helps rule out disease in both breasts and provides important information for surgical planning if needed. 

If the diagnostic mammogram confirms suspicious findings, the next step is typically a core needle biopsy. During this procedure, a small sample of breast tissue is taken from the area of concern and examined under a microscope. This breast biopsy helps determine if the abnormal cells are noninvasive (DCIS) or invasive breast cancer.

The pathologist also tests the tissue for hormone receptors for estrogen (ER) and progesterone (PR) as well as a protein involved in cell growth called HER2. Identifying these features may guide treatment, especially in cases where hormone therapy may reduce the risk of future cancer.

Ductal Carcinoma in Situ Symptoms

Ductal carcinoma in situ typically does not cause noticeable symptoms, such as a breast lump or pain. In most cases, DCIS is found during routine screening mammograms before any physical signs or symptoms appear.

In fact, almost all DCIS cases are detected this way. Because there is usually no palpable mass, many patients may be unaware of any changes in their breasts until a tumor shows up on imaging. This highlights the importance of regular breast cancer screenings.

Ductal Carcinoma in Situ Treatment

Treatment for DCIS typically involves either breast-conserving surgery (BCS) or a mastectomy. Many women are able to choose between these two options.

Breast-conserving surgery: In BCS, the surgeon removes the DCIS and a small amount of healthy tissue surrounding it. Radiation therapy usually follows this procedure to reduce the risk of the cancer coming back in the same breast. Lymph node removal is not generally necessary unless invasive cancer is found during or after surgery. In some cases, BCS without radiation therapy might be an option, especially for older women, those with significant health issues or those with small areas of low-grade DCIS.

Mastectomy: For women with larger areas of DCIS or multiple regions throughout the breast, a simple mastectomy, which removes the entire breast, may be recommended. A sentinel lymph node biopsy might also be performed during a mastectomy, especially if there is a higher chance that invasive cancer could be present.

For women with hormone receptor-positive DCIS, taking hormone-blocking medications like tamoxifen or aromatase inhibitors for five years after surgery may lower the risk of another DCIS or invasive cancer developing in either breast. These treatments target the hormones that may fuel breast cancer growth and reduce the chances of a recurrence.

Ongoing clinical studies are also exploring whether observation, rather than immediate breast cancer surgery, could be an option for certain women with DCIS.

Why Have a Mastectomy for DCIS?

Some women with DCIS choose a mastectomy, or their doctor may recommend it depending on certain factors.

• A mastectomy may be advised if the DCIS affects a large area of the breast, especially if the breast is small, making breast-conserving surgery (BCS) less practical.
• If DCIS is present in more than one area of the breast or located under the nipple, a mastectomy might be a better option.
• Additionally, if a woman is unable to undergo radiation therapy for breast cancer due to medical reasons or personal preference, a mastectomy may be recommended.
• Some women may opt for a mastectomy to reduce the risk of cancer returning in the affected breast.

Studies show that women who have BCS followed by radiation therapy have the same survival rates as those who choose mastectomy. This holds true whether or not they opt for breast reconstruction.

Women undergoing mastectomy often consider breast reconstruction surgery, which may be performed either at the same time as the mastectomy or later. Reconstruction helps restore the appearance of the breast after surgery.

Ductal Carcinoma in Situ Survival Rate

The five-year relative survival rate estimates how many people are still alive five years or more after being diagnosed with or starting treatment for a condition like cancer. It is expressed as a percentage and helps show how successful cancer treatments are over time.

For ductal carcinoma in situ (DCIS), the five-year relative survival rate is extremely high. In fact, for localized breast cancer, which includes DCIS, the five-year relative survival rate is 99.6%, according to the National Cancer Institute. This means that almost all women diagnosed with DCIS are still alive five years later.