Ductal carcinoma in situ (DCIS) is a non-invasive breast condition where some cells within the breast ducts (tubes that carry milk to the nipple) appear atypical. DCIS cells stay in the breast ducts and do not spread to other parts of the body. This characteristic makes DCIS very different from “invasive” breast cancer.
There are different “grades” of DCIS. The grade is determined by a pathologist (a physician who specializes in studying tissue) who looks at the appearance of the cells under a microscope.
You will sometimes hear DCIS described as low-risk. This includes both grades I and ll.
It is discussed further at the end of this section.
DCIS is most often found by mammograms in women who have no breast lumps or other symptoms. Micro-calcifications (tiny bits of calcium that appear as white dots on a mammogram) indicate the possible presence of DCIS.
About 10% of women with DCIS are diagnosed because of symptoms such as nipple discharge, a breast lump, or skin changes. Patients with DCIS associated with symptoms are thought to be at higher risk of poor outcomes if not treated.
While most DCIS is usually found on a mammogram (or in some cases when there are physical symptoms), other types of testing may be carried out to learn more about the condition or if there are specific indications that they are needed.
Ultrasound uses high frequency sound waves to produce detailed computer images of the inside of the breast. Ultrasound may be used to look at breast changes that can be felt but not seen on a mammogram, or if more information is needed about a change that may have been seen on a mammogram. A breast ultrasound is painless and does not use radiation. A breast ultrasound may be useful for:
- Women with dense breast tissue
- Women who are pre-menopausal or under age 50
- Women who are pregnant
- Women who are breast-feeding
- Women with silicone breast implants
Magnetic Resonance Imaging (MRI)
MRIs use radio waves and a magnet to create detailed pictures of the inside of the body. This can highlight tissue that does not appear to be normal. MRI is not routinely used to screen for DCIS. However, it can be used if irregular spots are found on a mammogram. An MRI can provide information about how much DCIS exists. An MRI is also used to help decide what kind of surgery may be needed (if any).
All of the imaging methods described here are used to screen for possible atypical cells. Women with suspicious findings on any of the examinations above will likely be referred for a biopsy. This is where a small amount of breast tissue is removed to check for cancer or other abnormalities. If DCIS is found, a pathologist measures the cells under a microscope to see if (and how) it is growing. The biopsy is used to provide important information and confirm a diagnosis.
There are two common types of breast biopsy. A core biopsy is where tissue is removed from a suspicious area of the breast with a needle. The core biopsy can either be directed with mammograms (stereotactic biopsy) or ultrasound (ultrasound-guided biopsy). This helps to identify any potential areas of concern. A further biopsy may be necessary if the core biopsy is not able to remove cells to give clear and definite results. If DCIS is diagnosed (or still suspected), a wider area of tissue may need to be removed. This is known as a surgical biopsy. It may also be called “wide local excision” or a “lumpectomy.”
A pathology report describes the specific characteristics of the tissue taken in the biopsy. Reading a pathology report and having confidence that it is correct is important since future treatment options will be based upon it. A copy of the report should be taken to any further consultations. A second pathology opinion may be requested.
A pathology report will state whether DCIS is low, intermediate, or high grade. There is a wide range of DCIS with different size, structure, and speed of growth. Based on these characteristics, the pathologist (a physician who specializes in studying tissue) will decide if you have DCIS and if so, will assign a grade.
Your pathology report should also include the results of a hormone test for estrogen and progesterone receptors (ER/PR). These receptors make the DCIS cells very sensitive to the hormones estrogen and progesterone. If the receptors are present it may be stated as ER/PR with a (+) for positive, meaning it is sensitive to hormones that may cause it to grow, or a (-) for negative, meaning it does not respond to these hormones. These results help you and your doctor decide whether your DCIS is likely to respond to endocrine (hormone-blocking) therapy.
The pathology report will also describe the margin. A margin is a small amount of tissue around the DCIS. If it is healthy with no evidence of DCIS, it is called a clear or clean margin. If some DCIS is found at the edge of this tissue, it is known as a positive margin and is a signal that there is likely more DCIS in the breast. Another surgery called a re-excision is then necessary to obtain a clear margin. The importance of getting clear or clean margins is to try and reduce the chances of any microscopic DCIS being left behind in that part of the breast.
If cells that do not appear normal are found outside the breast duct, it is called an invasive cancer and is no longer considered DCIS. This includes what is known as a “micro-invasion.” It is then “upstaged” from DCIS to invasive cancer and is treated as invasive breast cancer.
For more information, see ‘Understanding your Pathology Report.’
DCIS that may have the lowest chance of becoming invasive cancer is called low-risk DCIS. Low-risk DCIS is generally thought to be DCIS that is grade I or grade II, sensitive to hormones, and does not cause symptoms.
There is growing evidence suggesting that low-risk DCIS grows so slowly that it would never cause health problems during a woman’s lifetime. For this type of DCIS, surgery and radiation may have very little or no benefit. There is ongoing research to better understand low-risk DCIS and how best to treat it. You might want to discuss with your doctor whether you have low-risk DCIS. If you do, you may be eligible for a clinical trial. Three trials that compare surgery to monitoring (also known as “active surveillance”) for low-risk DCIS are currently underway. These include the COMET (Comparison of Operative to Monitoring and Endocrine Therapy for low-risk DCIS) Study in the US (see active surveillance menu item under the DCIS tab).