Ductal carcinoma in situ (DCIS)
This article was last reviewed and updated on August 13, 2019.
by Jason Wasserman, MD PhD FRCPC
Ductal carcinoma in situ (DCIS) is a non-invasive type of breast cancer.
It is called non-invasive because the cancer cells have not spread out of the ducts and glands into the surrounding breast tissue.
If left untreated, ductal carcinoma can lead to a more serious disease called invasive ductal carcinoma.
The normal breast
Adult breast tissue is made up of small structures called glands which are organized into groups called lobules. Under certain conditions, these glands can produce milk, which is transported to the nipple by a series of small channels called ducts.
The inside of both glands and ducts is lined by specialized cells called epithelial cells which form a barrier called the epithelium. The tissue surrounding glands and ducts is called stroma and contains long, thin cells called fibroblasts.
What is ductal carcinoma in situ?
Ductal carcinoma in situ is a type of non-invasive breast cancer. The tumour starts from the epithelial cells in the glands and ducts of the breast.
Ductal carcinoma in situ is called non-invasive because, after careful microscopic examination, cancer cells were found only on the inside of the ducts and glands.
If left untreated, patients with ductal carcinoma in situ are at high risk for developing a more serious disease called invasive ductal carcinoma. In contrast to ductal carcinoma in situ, the cancer cells in invasive ductal carcinoma have moved outside of the ducts and glands and into the surrounding stroma. The movement of cancer cells from the inside of the ducts and glands into the stroma is called invasion.
Because ductal carcinoma in situ is a non-invasive disease, the cancer cells are not capable of spreading to lymph nodes or other parts of the body.
How do pathologists make this diagnosis?
The diagnosis of ductal carcinoma in situ is usually made after a small sample of breast tissue is removed in a procedure called a core needle biopsy. The biopsy is then examined under a microscope by a pathologist. Surgery may later be performed to remove the entire tumour which is sent to a pathologist for examination.
Depending on the amount of breast tissue removed, the procedure may be called a 'lumpectomy' (literally removal of the 'lump') or a 'mastectomy'.
This is the size of the tumour measured in millimeters. Tumour size will only be described in your report after the entire tumour has been removed. The tumour is usually measured in three dimensions but only the largest dimension is described in your report. For example, if the tumour measures 40 millimeters by 20 millimeters by 15 millimeters, your report will describe the tumour as being 40 millimeters in greatest dimension.
Why is this important? Large tumours are more likely to grow back after treatment. Large tumours also increase the risk that cancer cells will be found at the cut edge of the tissue (see Margins below).
Grade is a word pathologists use to describe the difference between the abnormal cells and the healthy cells normally found in the breast. The nucleus is the part of the cell that contains most of the cells genetic material (the DNA). The nuclear grade can only be determined after tissue is examined under the microscope.
The abnormal cells in ductal carcinoma in situ are given a nuclear grade between 1 and 3 based on the shape and size of the nuclei and the number of abnormal cells dividing to creating new cells (mitotic figures).
Instead of a numerical grade (1 through 3), some pathology reports divide the grade in low, intermediate, and high.
Why is this important? The nuclear grade is important because grade 3 (high grade) ductal carcinoma in situ is associated with a higher risk of developing invasive cancer compared to grade 1 (low grade) ductal carcinoma in situ.
Necrosis is a type of cell death. Comedonecrosis is a special type of necrosis sometimes seen in ductal carcinoma in situ. In comedonecrosis, the dead cells are in the centre of a duct and surrounded by living cells.
Why is this important? Comedonecrosis is more likely to be seen in high grade ductal carcinoma in situ. It is also associated with an increased risk of cancer compared to ductal carcinoma in situ without comedonecrosis.
If more than one tumour is seen in your tissue sample, each tumour will be described in your report.
A margin is any tissue that was cut by the surgeon in order to remove the tumour from your body. Whenever possible, surgeons will try to cut tissue outside of the tumour to reduce the risk that any cancer cells will be left behind after the tumour is removed.
Your pathologist will carefully examine all the margins in your tissue sample to see how close the cancer cells are to the edge of the cut tissue. Margins will only be described in your report after the entire tumour has been removed.
A margin is considered positive when there are cancer cells at the very edge of the cut tissue.
A negative margin means there were no cancer cells at the very edge of the cut tissue. If all the margins are negative, most pathology reports will say how far the closest cancer cells were to a margin. The distance is usually described in millimeters.
Why is this important? A positive margin is associated with a higher risk that the tumour will grow back (recur) in the same site after treatment.
If you received treatment (either chemotherapy or radiation therapy) for your cancer prior to the tumour being removed, your pathologist will examine all of the tissue submitted to see how much of the tumour is still alive (viable).
The treatment effect will be reported as follows:
No residual tumour - all the cancer cells are dead
Probable effect - some of the cancer cells are dead but some are still alive
No definitive response - most of the cancer cells are still alive
Lymph nodes with cancer cells will also be examined for treatment effect.
Estrogen receptor (ER) and progesterone receptor (PR) status
Estrogen and progesterone receptors are proteins that are produced by normal breast cells which allow the cells to respond to the hormones estrogen and progesterone.
Your pathologist will test your tumour to see if it makes ER or PR. Tumours that make ER or PR are said to be hormone positive. Tumours that do not make ER or PR are called hormone negative.
Why is this important? Tumours that make ER or PR are treated with special medication that targets the activity of these proteins. After reviewing your pathology report, your doctor will talk with you about the treatment options best suited for you.
Lymph nodes are small immune organs located throughout the body. Cancer cells can travel from the tumour to a lymph node through lymphatic channels located in and around the tumour. The movement of cancer cells from the tumour to a lymph node is called a metastasis.
Lymph nodes are not always removed for ductal carcinoma in situ. However, if lymph nodes are removed, each lymph node will be carefully examined for cancer cells. Lymph nodes that contain cancer cells are often called positive while those that do not contain any cancer cells are called negative. Most reports include the total number of lymph nodes examined and the number, if any, that contain cancer cells.
There are three types of lymph nodes that may be described in your report:
Sentinel axillary lymph node - This is the first lymph node in the chain of lymph nodes that drains fluid from the breast. If cancer is going to be found in the axilla, it will usually be found in the sentinel node first.
Non-sentinel axillary lymph node - This type of lymph node is located after the sentinel lymph node in the axilla. Cancer cells usually travel to these lymph nodes after passing through the sentinel lymph node.
Internal mammary lymph node - This type of lymph node is found in the breast itself. Cancer cells may travel to these lymph nodes if the lymph node is found close to the tumour.
If cancer cells are found in a lymph node, the size of the area involved by cancer will be measured and described in your report as follows:
Isolated tumour cells - The area of tumour cells measure less than 0.2 millimeters and have less than 200 tumour cells.
Micrometastases - The area of tumour cells measures more than 0.2 millimeters but less than 2 millimeters.
Macrometastases - The area of tumour cells measures more than 2 millimeters.
Why is this important? Finding cancer cells in a lymph node is associated with an increased risk that the cancer will come back at a distant body site such as the lungs in the future. This information is also used to determine the nodal stage (see Pathologic stage below).
The pathologic stage for ductal carcinoma in situ is based on the TNM staging system, an internationally recognized system originally created by the American Joint Committee on Cancer.
This system uses information about the primary tumour (T), lymph nodes (N), and distant metastatic disease (M) to determine the complete pathologic stage (pTNM). Your pathologist will examine the tissue submitted and give each part a number. In general, a higher number means more advanced disease and worse prognosis.
Tumour stage (pT) for ductal carcinoma in situ
Ductal carcinoma in situ is a non-invasive form of cancer and is given the tumour stage pTis.
Nodal stage (pN) for ductal carcinoma in situ
Ductal carcinoma in situ is given a nodal stage between 0 and 3 based on the number of lymph nodes that contain cancer cells, the amount of cancer cells found in the lymph node, and the location of the lymph nodes with cancer cells.
Because ductal carcinoma in situ is a non-invasive form of cancer, cancer cells are rarely found in a lymph node and most cases are given a nodal stage of pN0.
N0 - No cancer cells are found in any of the lymph nodes examined.
N0(i+) - Only isolated cancer cells were found in a lymph node.
N1mi - Micrometastases. Cancer cells were found in a lymph node but the group of cancer cells is not bigger than 2.0 millimeters.
N1a - Cancer cells were found in 1 to 3 lymph nodes from the axilla (under the arm) and at least one group of cancer cells is larger than 2.0 millimeters.
N1b - Cancer cells were found in an internal mammary sentinel lymph node.
N1c - Cancer cells were found in a lymph node from the axilla and an internal mammary lymph node.
N2a - Cancer cells were found in 4 to 9 axillary lymph nodes and at least one group of cancer cells was larger than 2.0 millimeters.
N2b - Cancer cells were found in internal mammary lymph nodes after imaging of the breast.
N3a - Cancer cells were found in 10 or more axillary lymph nodes and at least one group of cancer cells is larger than 2.0 millimeters OR cancer cells were found in a lymph node below the clavicle.
N3c - Cancer cells were found in a lymph node above the clavicle.
If no lymph nodes are sent for pathological examination, the nodal stage cannot be determined and the nodal stage is listed as pNX.
Metastatic stage (pM) for ductal carcinoma in situ
Ductal carcinoma in situ is given a metastatic stage of 0 or 1 based on the presence of cancer cells at a distant site in the body (for example the lungs). The metastatic stage can only be determined if tissue from a distant site is submitted for pathological examination. Because this tissue is rarely sent, the metastatic stage cannot be determined and is listed as pMX.