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Ductal Carcinoma In Situ (DCIS)

What is Ductal Carcinoma In Situ?
Ductal carcinoma in situ (pronounced DUCKtul carsinOHMa inSIGHT-to) is often abbreviated and spoken as the letters DCIS.
Ductal carcinoma in situ is a highly curable form of early breast cancer. The name means 'duct cancer in the original place' and refers to the fact that the cancer started inside the milk duct and remains confined there.
A breast cancer can only threaten life by spreading beyond the breast to other organs. It does this by entering a blood or lymph vessel in the breast. These vessels are channels that cancer cells use like highways to leave the breast. All of these channels are located outside of the
breast ducts
. If the cancer cells are only inside the breast duct, they cannot enter these channels and they cannot spread beyond the breast. That is the case with ductal carcinoma in situ.
If under-treated, some cases of

ductal carcinoma in situ

can change and become more aggressive. They 'learn' how to invade through the duct and then become an

invasive breast cancer

that can then enter blood or lymph channels and spread to other organs. The main goal of

treatment of ductal carcinoma in situ

is to prevent this from happening.
Some doctors describe ductal carcinoma in situ as a 'pre-cancerous' condition. They do this with the good intention of emphasizing the excellent cure rate. But this is not correct. Ductal carcinoma in situ is a cancer, but one with an extremely high cure rate. By calling it pre-cancerous, patients and doctors may be distracted from giving it the attention it deserves. This may lead to under-treatment. Under-treating ductal carcinoma in situ may increase the future risk of developing a life-threatening invasive breast cancer.

How is Ductal Carcinoma In Situ Diagnosed?

Ductal carcinoma in Situ calcification on mammogram.
Illustration: DCIS calcifications as shown on a mammogram.
Most cases of ductal carcinoma in situ are detected by
screening mammograms
. It most commonly appears as a small sprinkling of tiny white dots of calcium on the mammogram. These are called 'clustered micro-calcifications'. It may also appear without micro-calcifications as a shadow or mass on the mammogram. Breast ultrasound and MRI may sometimes help identify ductal carcinoma in situ, particularly in younger women with dense breasts for whom mammograms may be less effective.
The first step in diagnosing any breast cancer is a needle biopsy. Jumping to surgical removal of the lump - before needle biopsy has confirmed it to be a cancer - is a natural reflex for many patients and doctors. "I just want it out!" This reflex is understandable, but it's not the best first step. There are very good reasons for doing needle biopsy before surgical removal. It may allow the patient to undergo one surgery for treatment rather than two. It's even possible that the treatment will be more successful if a needle biopsy is done first.

How is Ductal Carcinoma In Situ Treated?

Removal of the area (or mass) of ductal carcinoma in situ is the main treatment. There are two different strategies of treatment. The first is mastectomy: complete surgical removal of the breast. Mastectomy is very effective therapy for ductal carcinoma in situ, but it is disfiguring. It is also an unnecessarily radical surgery for most cases of ductal carcinoma in situ. There is an excellent alternative to mastectomy for women with ductal carcinoma in situ that avoids a disfiguring surgery. That alternative is the combination of lumpectomy followed by radiation therapy. Lumpectomy is removal of the cancerous area only and is also called a partial mastectomy. The combination of lumpectomy and radiation therapy is called breast conservation therapy. Breast conservation therapy offers the same ultimate cure rate as mastectomy for most women with ductal carcinoma in situ.
In a lumpectomy, the area of ductal carcinoma in situ is removed with a small amount of normal tissue around it. Lumpectomy alone is inadequate; experience tells us that an invisibly small number of cancer cells sometimes remain at the edge of the surgery site. After lumpectomy alone for ductal carcinoma in situ, some patients experience a re-growth of the cancer at the site of the original surgery. This is called a local recurrence. Trying to remove a larger amount of breast tissue to prevent this would leave a deformed breast and defeat the purpose of breast conservation.
Fortunately, moderate doses of radiation therapy are extremely effective in wiping out the small amounts of residual ductal carcinoma in situ that remain at the edge of the surgery site. This radiation therapy can be delivered by external beam treatments delivered once daily for an average of six weeks, or by newer more targeted breast brachytherapy (internal radiation) techniques that are completed in one week.
Almost all women with ductal carcinoma in situ are appropriate for breast conservation with lumpectomy and radiation and should be offered this option.
Some women may be offered lumpectomy alone for their diagnosis of ductal carcinoma in situ. Omitting radiation therapy after a lumpectomy increases the chances of the ductal carcinoma in situ growing back in the area of the scar. When it does grow back, it can sometimes change into a more aggressive and potentially life-threatening invasive cancer. While some women may be appropriately treated with lumpectomy alone for ductal carcinoma in situ, it is not the best treatment for most women with this disease. Mastectomy and breast conservation (lumpectomy and radiation therapy) remain the two best treatment options.
Chemotherapy is only used for invasive breast cancer and has no role in the treatment of ductal carcinoma in situ. Estrogen blocking drugs (tamoxifen, letrozole, anastrazole, etc) may slightly reduce the risk of a recurrence of ductal carcinoma in situ, but these drugs are more effective in preventing new breast cancers from forming in either breast. For this reason, one of these estrogen-blocking drugs is sometimes offered as breast cancer prevention therapy after lumpectomy and radiation therapy for ductal carcinoma in situ.

Summary of Ductal Carcinoma In Situ

Ductal carcinoma in situ is a highly curable form of early breast cancer. Because the cancer is confined to the milk duct, it cannot escape the breast and spread to other organs. It is most often diagnosed on a screening mammogram, and needle biopsy before surgical removal is the best approach. If treated appropriately with mastectomy or breast conservation (lumpectomy followed by radiation), the cure rate is 99%. If under-treated, ductal carcinoma in situ can grow back as a potentially life-threatening invasive breast cancer.