Ductal carcinoma in situ of the breast (DCIS)

What is ductal carcinoma in situ?

Ductal carcinoma in situ (DCIS) is a non-invasive type of breast cancer. The tumour starts from specialized cells in the glands and ducts of the breast (see pictures below). 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.

The 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.

 

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’ or a ‘mastectomy’.​

ductal carcinoma in situ

Nuclear grade

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 genetic material (the DNA).

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. This process is called mitosis and a cell that is dividing is called a mitotic figure. The nuclear grade can only be determined after the tissue is examined under the microscope.

Instead of a numerical grade (1 through 3), some pathology reports divide the grade into low, intermediate, and high.

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.

Comedonecrosis

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 center of a duct and surrounded by living cells. 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.​​

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 the 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.

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.

What to look for in your report after the tumour has been removed

Tumour size

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 the greatest dimension. 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).

Multiple tumours​

If more than one tumour is seen in your tissue sample, each tumour will be described in your report.

Margins

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.

Margin

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 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 millimetres. A margin is considered positive when there are cancer cells at the very edge of the cut tissue. A positive margin is associated with a higher risk that the tumour will grow back (recur) in the same site after treatment.

Treatment effect

​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). Lymph nodes with cancer cells will also be examined for treatment effect.

The treatment effect will be reported as follows:

  1. No residual tumour – All the cancer cells are dead.
  2. Probable effect – Some of the cancer cells are dead but some are still alive.
  3. No definitive response – Most of the cancer cells are still alive.
Lymph nodes

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 metastasis.

Lymph node

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.

Finding cancer cells in a lymph node is associated with an increased risk that 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).

Pathologic stage

​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 a 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.

Breast pathologic stage Tis

Nodal stage (pN) for ductal carcinoma in situ

Ductal carcinoma in situ is a non-invasive type of cancer. For this reason, it is very rare to find cancer cells in a lymph node. However, if cancer cells are found in one or more lymph nodes your pathologist will provide a nodal stage between 0 and 3 based on the number of lymph nodes that contain cancer cells, the number of cancer cells found in the lymph node, and the location of the lymph nodes with cancer cells.

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). Because ductal carcinoma in situ is a non-invasive type of cancer. For this reason, it is very rare to find cancer cells in another part of the body. 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.

by Jason Wasserman MD PhD FRCPC (updated July 2, 2021)
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