What To Know About Ductal Carcinoma In Situ (DCIS)

It Affects Cells In The Milk Ducts

Each breast has about 15 to 20 milk ducts, which, in women, act as a canal system to transport milk to nursing babies. DCIS occurs when cells in one of those milk ducts have mutated and multiplied to look like cancer cells.

About one in five newly diagnosed breast cancers is DCIS, per Johns Hopkins Medicine. Because those cells usually stay confined to the duct and do not spread to surrounding tissue, DCIS is also known as stage 0 breast cancer or sometimes pre-cancer. (The words "in situ" mean "in its original place," indicating that the cancerous cells don't leave the duct.)

It's Usually Found On A Mammogram

For most women, DCIS is picked up on routine mammograms. "Typically, the mammogram finds a calcification—a small cluster of cells with abnormal shapes and sizes—and then it is diagnosed after a biopsy," Dr. Meyers said.

Occasionally, though, DCIS grows large enough that it forms a noticeable lump. Some people with DCIS may also have unusual nipple discharge, or a condition called Paget's disease that causes skin around the nipple to become thick and dry according to the National Cancer Institute (NCI).

Diagnoses Have Increased

"We've seen a huge increase in the number of DCIS cases diagnosed in the last 20 years," Julia White, MD, director of breast radiation oncology at the Ohio State University Comprehensive Cancer Center, told Health.

In the 1990s, only about 15,000 to 18,000 DCIS cases were diagnosed per year, Dr. White said. That number has grown to more than over 50,000 according to the ACS. "That's because so many women are now getting mammograms, and the technology is so good, that we pick up very small lesions," Dr. White explained.

As a result, women are getting treated earlier than ever, which means there are fewer chances for DCIS to break out of the milk duct and become invasive. (This happens in anywhere from 20% to 50% of untreated DCIS lesions, according to the ACS.) However, there's no way to tell which lesions will become invasive, so some experts have said there's a real danger of overdiagnosis and unnecessary treatment.

Prognosis Is Excellent

Because DCIS is noninvasive, patients' chances of recovery and long-term survival after treatment are great.

After 10 years of follow-up, the percentage of survival has been approximately 98% according to the authors of a July 2019 British Journal of Cancer article.

Additionally, prognosis was also "extremely good, " per an August 2021 article published in Virchows Archiv, for women whose DCIS diagnosis with managed with approaches such as surgical excision, radiotherapy, and endocrine therapy.

After DCIS, The Risk Of Another Cancer Is Higher

Stage 0 breast cancer still comes with risks. "When you have DCIS, it means your risk of developing another DCIS or an invasive breast cancer is higher than the general population," Dr. Meyers said.

In a May 2020 BMJ study, the researchers found that in comparison to women in the general population, women who were diagnosed with DCIS were more at long term risk for invasive breast cancer and death due to breast cancer within 20 years of finding the diagnosis detected during a breast cancer screening.

"Whatever caused the cells to mutate will generally occur in more than one duct—and sometimes, those mutated cells can break through a duct and become invasive breast cancer," Dr. Meyers added. "We don't know why some [cases of] DCIS have the ability to do this while others don't, so right now we want to treat all of them with at least surgery, and maybe more."

Tumor Size Matters

After a woman is diagnosed with DCIS and has the abnormal growth removed via surgery, the next step is to assess her risk of a recurrence or a more invasive cancer.

One important factor in that calculation is the size of the DCIS, Dr. White said. "With DCIS lesions [bigger] than 20 to 25 millimeters, the general recommendation is for more than just surgery," Dr. White explained. That additional treatment may include radiation and hormone therapy.

"Nuclear Grade" of DCIS Matters Too

Healthcare providers will also consider the nuclear grade of DCIS, which is determined by looking closely at the nuclei of the cells removed during a biopsy. According to the ACS, there are three grades of DCIS: low, or grade 1 (which look the most like normal, healthy cells); moderate, or grade 2; and high, or grade 3 (which look the most abnormal and grow the fastest).

High-grade DCIS is sometimes described as "comedo" or "comedo necrosis," which means that dead cells have built up inside the fast-growing tumor. The higher the grade, the greater chance a person has of also having invasive breast cancer, either with the DCIS or at some point in the future.

A Test Can Help You Determine Your Risk

Sometimes healthcare providers will recommend a genomic test, called the Oncotype DX test, to help determine a DCIS patient's risk of getting another cancer in the future. A sample from the DCIS biopsy or lumpectomy is sent to a lab, where pathologists study the activity of 12 different cancer-related genes.

"You get back what's called a DCIS score, from zero to 100, that tells you the likelihood of a DCIS recurrence or of an invasive cancer in the next 10 years," Dr. White said. "I want to help patients keep their breasts, so if they have a high risk of recurrence we want to recommend radiation so they can prevent that invasive cancer in the future."

Memorial Sloan Kettering Cancer Center has also developed a free online assessment tool to helps DCIS patients estimate their risk of another cancer, based on age, family history, and details about their specific tumor. "We want to help patients understand their individual risks, so they can make an informed decision about how much treatment they're going to have," Dr. White said.

DCIS Can Be Removed With Surgery

DCIS can often be removed via a lumpectomy, per MedlinePlus, which is a surgery that spares the surrounding breast tissue. (In some cases, if DCIS has infiltrated multiple ducts or a tumor has grown large enough, removing the entire breast via mastectomy may be recommended.)

When performing a lumpectomy, surgeons aim to remove all of the cancerous cells, plus a two-millimeter margin of healthy cells around the tumor. This helps ensure that the cancer is 100% removed, and lowers the risk of a recurrence.

Because some DCIS may never progress, some patients may also opt to skip surgery, adopting a watch-and-wait approach instead.

Some People With DCIS Get Radiation

Next, healthcare providers and patients should decide together whether further treatment is needed to reduce the risk of another DCIS or an invasive cancer. This can be determined through genomic testing, or by looking at factors like the patient's age, family history, and tumor size and grade.

"Several years ago, radiation would have been given to everyone who had DCIS, period," Dr. Meyers said. "But now, it's a little more tailored to the type of DCIS and the type of patient, and there's been a downward trend of getting less radiation or avoiding it completely, if possible."

Radiation does come with side effects—and it has not been shown to extend survival in patients with DCIS; it's only been shown to reduce the risk of another cancer occurring. So patients should weigh the pros and cons carefully, Dr. Meyers added, and make the best individual decision for them.

Others Take Hormone-Blocking Medicines

For some people with DCIS, taking drugs that block the production of sex hormones—like tamoxifen or aromatase inhibitors—can also reduce the risk of a DCIS recurrence or a future invasive cancer. But these medicines also cause side effects, and they won't lower the risk for everyone.

In order to tell if these drugs will be effective, a DCIS tumor should be tested to see if it has estrogen and progesterone receptors. "The majority of women will have positive hormone receptors," Dr. Meyers said. "But for those who don't, we don't do risk reduction with these drugs because they're not likely to be advantageous."

Like radiation, these drugs have not been shown to actually extend the survival rate of patients with DCIS—only to reduce the risk of another cancer. Patients should consider their individual risk factors to decide whether additional treatment is worth it to them, Dr. Meyers said, "and if they feel miserable on these medicines, we can always stop them."

Chemo Isn't Necessary

Because DCIS is non-invasive, chemotherapy—which sends cancer-killing drugs throughout the body and can have side effects including nausea and vomiting, hair loss, fatigue, and fertility problems—is not used as a treatment option.

Very rarely (in less than 1% of all cancer diagnoses), pathology reports show that cancer cells in a DCIS lesion have started to break through the wall of the duct, known as DCIS with microinvasion, or DCIS-MI. A March 2016 CancerBiology and Medicine study suggested that chemotherapy may be beneficial in these cases, but more research is still needed.

Men Can Get It Too

Yes, men have milk ducts—and occasionally, those ducts can develop cancer just like a woman's. Men can get DCIS, but it's rare as it shows up in around 1 in 10 cases per the ACS. And because they don't get routine mammograms, breast cancer of any kind often isn't discovered in men until it has already reached a later stage, when the tumors are large enough to be felt during a physical exam.

Once DCIS is discovered in a man, treatment and prognosis are generally the same as they would be for a woman with a similar size and grade tumor, Dr. Meyers explained.

DCIS Can Happen At Any Age

"DCIS can happen to anybody, anytime," Dr. Meyers said, but it's usually diagnosed in women over 40, the age at which many women begin getting mammograms. According to the ACS, DCIS rates increase with age and peak around age 70 to 79.

Women diagnosed with DCIS under age 50 have a higher rate of recurrence or of an invasive cancer, and therefore more aggressive treatment is usually recommended, Dr. White said. Those over 50, on the other hand, can take comfort in knowing that a diagnosis does not raise their risk of early death.

DCIS Has The Same Risk Factors As Invasive Breast Cancers

"The same things that increase a woman's risk for DCIS are really the same things that increase her risk of invasive breast cancer," Dr. Meyers said. For example, having a strong family history can be a factor—especially if a woman tests positive for a high-risk BRCA gene mutation.

Women who have a longer period of estrogen stimulation, meaning they started menstruation early and/or entered menopause late, also have an increased risk of DCIS as well as invasive cancer. That also goes for women who don't have children or who have their first pregnancy after age 30.

Lifestyle Also Plays A Role

Some risk factors for DCIS are modifiable. Eating lots of fruits and vegetables, maintaining a healthy weight, and limiting alcohol intake have all been linked to lower breast cancer rates, Dr. Meyers said, and they are smart habits to develop no matter what type of breast cancer you're trying to avoid.

For women who have already had DCIS, cutting back on drinking may reduce their risk of a recurrence, according to a January 2014 study in the journal Cancer, Epidemiology, Biomarkers & Prevention. "It is possible that alcohol consumption may increase risk of second breast cancer incidence," the authors wrote in their paper, "but may not substantially increase the likelihood of aggressive second diagnoses that result in death, particularly among DCIS survivors."

You Can Still Breastfeed After DCIS

Even though DCIS affects the milk ducts, it doesn't necessarily mean a woman can't produce milk if she gets pregnant after diagnosis and treatment. "As long as a woman has surgery alone, and assuming the lesion is not too close to the nipple, DCIS should not cause problems with conceiving or breastfeeding," Dr. Meyers explained.

If a woman has been treated with radiation or hormone therapy in addition to surgery, on the other hand, "we usually recommend that a woman see her gynecologist or a fertility doctor to ensure there won't be an issue," Dr. Meyers added.

It Can Be a Controversial Diagnosis for Healthcare Providers

A study published in the May 2016 issue of the Annals of Internal Medicine journal found that pathologists disagree with one another about 8% of the time when diagnosing breast biopsy samples, and that cases of DCIS were the most difficult to reach a conclusion about. About 19% of DCIS cases were overinterpreted in the study, meaning they were mistakenly categorized at a higher grade or as invasive cancer, and about 12% were underinterpreted, or mistakenly categorized at lower grades.

The authors wrote that non-invasive breast lesions represent a "gray zone" in medicine, where there's not always a right or wrong diagnosis. They said that revised guidelines are needed to make sure DCIS patients get a consistent diagnosis they can trust.

A Vaccine May Be Helpful

Patients diagnosed with DCIS may one day get a vaccine to help reduce their risk of developing an invasive breast cancer in the future, according to a December 2016 study published in Clinical Cancer Research.

More clinical trials are underway, but researchers have been hoping that a vaccine may be able to stimulate the immune system and keep early DCIS from progressing beyond the milk duct. If trials are successful, experts said it could eventually be an alternative to surgery and radiation for some patients.