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Ductal carcinoma in situ (DCIS) involves abnormal cells that form in a milk duct in your breast. Because these abnormal cells haven’t spread beyond the milk duct to the surrounding tissue, it has a high cure rate.

DCIS is considered a stage 0 or preinvasive cancer. In other words, it’s a precursor to breast cancer.

In this article we’ll take a closer look at DCIS as well as the known risk factors, treatment options, and the outlook.

Your breasts are made of three different types of tissue:

  • lobes (which are made up of smaller sacs called lobules, which make milk)
  • ducts (which transport milk to your nipple)
  • fatty or fibrous connective tissue
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Credit: Wenzdai Figueroa

DCIS happens when a group of abnormal cells starts growing inside the lining of a milk duct. Because these cancerous cells haven’t spread beyond the duct to other breast tissue, it’s known as a preinvasive or noninvasive cancer.

Sometimes, especially if these abnormal cells aren’t treated early on, they can become an invasive form of breast cancer. Invasive breast cancer has the capacity to spread to other parts of your body. When this happens, the breast cancer is said to have metastasized.

According to the American Cancer Society, DCIS accounts for about 16 percent of all breast cancer diagnoses in the United States.

You can’t usually see or feel the abnormal cells in your milk duct. As a result, you may not have any symptoms. In fact, in the vast majority of cases, DCIS is detected during a breast cancer screening using a mammogram.

The abnormal cells typically show up on a mammogram as clusters of bright white flecks (known as microcalcifications) with irregular shapes.

In some cases, DCIS may cause symptoms such as:

  • discharge coming from a nipple that isn’t milk
  • a small lump

Most breast symptoms or changes aren’t caused by cancer, but tests are often needed to rule out the possibility of abnormal breast cells.

Exactly what causes DCIS isn’t known. Still, research has shed light on some of the possible factors that may increase your risk of developing a breast cancer diagnosis.

It’s important to know that your risk of developing breast cancer isn’t usually dependent on a single factor. You may have several risk factors, but that doesn’t necessarily mean you’ll get breast cancer.

However, understanding your risk factors can help you make better decisions about your health and healthcare.

The following factors may contribute to a higher risk of breast cancer:

Risk factors you can’t control

  • Being older. Most people diagnosed with breast cancer are older than 50 years of age.
  • Your genes. Genetic mutations, especially those associated with BRCA1 and BRCA2 genes, can increase your risk of cancer.
  • Longer-term exposure to hormones. If you started having periods before 12 years old or if you began menopause after 55 years old, you may have a higher risk of breast cancer.
  • Dense breast tissue. Breasts with a high concentration of connective tissue may be at a higher risk of breast cancer. The dense tissue can make it harder to see problem areas on a mammogram.
  • Personal history of breast disease. A history of atypical hyperplasia or lobular carcinoma in situ may increase your risk of breast cancer.
  • Family history of breast or ovarian cancer. Having a close relative (parent, sibling, child) who had breast or ovarian cancer raises your risk.
  • Radiation therapy. A 2017 study showed that if you had radiation therapy to treat another condition and your breasts were in the radiation field, your risk of breast cancer may be higher.
Healthline

Some risk factors — your age, for example — are things beyond your control. But some aspects of your lifestyle can affect your overall health and your risk of developing breast cancer.

Lifestyle risk factors

  • Hormone therapies. A 2019 meta-analysis and a 2018 research review showed that you may have a higher breast cancer risk if you take combined estrogen and progesterone hormone replacement therapy (HRT), or use certain birth control pills for a prolonged period of time.
  • Alcohol use. Alcohol intake has been associated with an increased risk of developing breast cancer.
  • Weight. Obesity can raise your risk of getting breast cancer, and it may also reduce the effectiveness of some breast cancer treatments, according to a 2019 research review.
  • Physical activity. A 2017 research review showed that a sedentary lifestyle may raise your breast cancer risk.
  • Pregnancy and breastfeeding. A 2014 research review showed that you may have a higher risk of developing breast cancer if your first pregnancy was after 30 years old, or if you never carried a pregnancy to term. Not chestfeeding may also increase your risk.
Healthline

Most of the time, DCIS is diagnosed through a routine breast cancer screening.

If your doctor thinks you might have DCIS, you’ll probably need further tests to confirm the diagnosis. These tests may include:

The report that comes back from the pathologists in the lab may contain some unfamiliar terms, like the ones described below:

  • High-grade, nuclear grade 3, and high mitotic rate describe DCIS that has a higher likelihood of developing again after treatment.
  • Intermediate-grade, nuclear grade 2, and intermediate mitotic rate are terms that indicate DCIS is a little less likely to return after treatment.
  • Low-grade, nuclear grade 1, and low mitotic rate describe DCIS that is least likely of the three to come back after treatment.
Healthline

A biopsy will also be able to determine the hormone receptor status of the DCIS cells. Many times, DCIS will have receptors that respond to the hormones estrogen or progesterone.

If these hormone receptors are present, it can help your doctor decide whether to offer you anti-estrogen medication to reduce the risk of recurrence.

Because DCIS involves the diagnosis of abnormal cells at a very early stage, treatments are usually highly effective.

Also, since the abnormal cells are only found in your breast duct, chemotherapy is never needed for DCIS.

Let’s take a closer look at some treatment options you and your healthcare team may decide to use, based on your specific diagnosis and situation.

Lumpectomy

Sometimes called breast-conserving surgery, a lumpectomy removes the tissue that contains the abnormal cells along with some surrounding tissues.

A lumpectomy preserves as much of your breast as possible. It’s often followed with radiation therapy which helps reduce the risk of the DCIScoming back.

Mastectomy

This type of surgery removes as much of the breast tissue as possible.

If DCIS is present in more than one place in your breast, or if there is a large area of DCIS, mastectomy may be the best option for your treatment.

Radiation therapy

Radiation therapy is often used after a lumpectomy to reduce the risk of the DCISreturning.

Radiation therapy uses high energy beams to damage the DNA of cancer cells. This helps to destroy the abnormal cells.

Radiation therapy is a localized type of treatment, which means it only targets the specific area that’s being radiated. This helps limit the damage to healthy cells.

Hormone therapy

Hormone therapy is an option if your cancer cells are hormone-receptor-positive. This means the cancer cells grow in response to estrogen or progesterone.

Hormone therapy can be added to your treatment plan after surgery to lower your risk of DCIS recurring in the future.

Two commonly prescribed hormonal therapies include:

  • Tamoxifen (an oral hormone) is an estrogen receptor blocker. By attaching to the cancer cells’ receptors in place of estrogen it helps block the growth signal to these cells.
  • Aromatase inhibitors are medications that help reduce how much estrogen is produced in the body after menopause.

The survival rate for people diagnosed with DCIS is very good.

A 2015 study that reviewed data involving 100,000 women over a 20-year span found that only 3.3 percent of women treated for DCIS later died from breast cancer, no matter what kind of treatment they had.

An important note

Women diagnosed with DCIS before 35 years old and Black women have a higher risk of death from breast cancer later in life, roughly 7 percent compared to 3 percent overall.

It’s important to note that the stress of enduring racism, discrimination, and racist systems may play a part in developing the disease beyond genetic factors.

After your DCIS treatment, it’s important to follow up with your healthcare team regularly to get regular screenings to make sure the cancer cells don’t return.

Ductal carcinoma in situ (DCIS) is a preinvasive breast cancer that has a very high cure rate. DCIS generally doesn’t have any symptoms and is most often detected during a mammogram.

Depending on the size and location of the affected cells, treatment of DCIS may involve a lumpectomy or mastectomy. Treatment could also include radiation and hormone therapy to prevent the cancer cells from returning.

Overall, DCIS has a very good outlook.