by Jason Wasserman MD PhD FRCPC
July 15, 2024
Ductal carcinoma in situ (DCIS) is a non-invasive type of breast cancer. The tumour starts from specialized epithelial cells in the glands and ducts of the breast. DCIS 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 DCIS are at high risk for developing a more serious disease called invasive ductal carcinoma.
Ductal carcinoma in situ (DCIS) often does not cause any symptoms and is typically detected during routine mammograms. However, some patients may experience the following symptoms:
The exact cause of DCIS is not well understood, but several factors may contribute to its development:
Several genetic syndromes and mutations are associated with an increased risk of developing DCIS:
Women with these genetic syndromes should consider genetic counselling and may need more frequent or earlier breast cancer screening.
Yes. DCIS is a non-invasive type of breast cancer. It is called non-invasive because the tumour cells have not spread beyond the ducts and glands into the surrounding breast tissue.
Ductal carcinoma in situ (DCIS) is indeed associated with an increased risk of developing more aggressive breast cancer. DCIS is a non-invasive form of breast cancer where abnormal cells are confined to the milk ducts and have not invaded surrounding breast tissue. However, if left untreated or inadequately treated, DCIS can progress to invasive ductal carcinoma (IDC), which is a more aggressive and potentially life-threatening form of breast cancer.
Regarding the risk of developing invasive breast cancer, it primarily affects the same breast where the DCIS was initially diagnosed. Studies have shown that women with DCIS have an increased risk of recurrence in the same breast, which can present as either DCIS again or as invasive breast cancer. The risk of developing invasive cancer in the contralateral (opposite) breast is also increased but to a lesser extent compared to the ipsilateral (same) breast.
The diagnosis of DCIS 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’.
Your pathologist will carefully examine the tissue under the microscope to see where the tumour cells are located within the breast. To make the diagnosis of DCIS, all of the tumour cells must be located inside the ducts. This is important because if any tumour cells are found outside the ducts, the diagnosis changes to invasive ductal carcinoma.
Pathologists divide DCIS into three levels or grades: grade 1 (low), grade 2 (intermediate), and grade 3 (high). They determine the grade for DCIS by looking at a part of the cell called the nucleus and comparing it to the cells normally found in the breast. They also look for the number of mitotic figures (tumour cells dividing to create new tumour cells).
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.
The solid type of DCIS is characterized by the proliferation of tumour cells that fill the entire ductal space without forming any secondary lumina or spaces within the ducts. The cells appear tightly packed together, forming a solid mass. Due to its dense cellularity, this type can sometimes be more challenging to distinguish from invasive ductal carcinoma.
In the cribriform type, the cancer cells proliferate in a way that creates multiple, evenly spaced, round spaces or “punched-out” holes within the ducts, resembling a sieve or “Swiss cheese” pattern. A uniform layer of epithelial cells surrounds these spaces. The cribriform pattern is generally considered to have a lower risk of progression to invasive ductal carcinoma than other types.
The micropapillary type features tufts of epithelial cells that extend into the lumen of the duct without a fibrovascular core. These tufts resemble small, finger-like projections or fronds. The absence of a fibrovascular core distinguishes micropapillary from papillary DCIS (see below). This subtype is associated with a higher risk of progression to invasive ductal carcinoma.
In the papillary type, the tumour cells form complex, branching structures that protrude into the ductal lumen. These papillary structures are supported by fibrovascular cores, which provide a blood supply to the proliferating cells. This type can occasionally be mistaken for intraductal papilloma, a benign condition, but papillary DCIS lacks the myoepithelial cell layer typical of benign lesions.
Comedonerosis is a term that describes dead tumour cells in the centre of a duct. It is more likely to be seen in grade 3 (high nuclear grade) DCIS. It is also associated with an increased risk of invasive ductal carcinoma compared to DCIS without comedonecrosis.
ER (estrogen receptor) and PR (progesterone receptor) are proteins in some breast cancer cells. These receptors bind to the hormones estrogen and progesterone, respectively. When these hormones attach to their receptors, they can stimulate cancer cells to grow. The presence or absence of these receptors can classify DCIS, which is important for determining treatment options and prognosis.
The presence of ER and PR in breast cancer cells means the cancer is hormone receptor-positive. This type of cancer is often treated with hormone (endocrine) therapy, which blocks the cancer cells’ ability to use hormones. Common hormone therapies include tamoxifen, aromatase inhibitors (such as anastrozole, letrozole, and exemestane), and drugs that lower hormone levels or block the receptors. Hormone receptor-positive cancers often respond well to these therapies.
Hormone receptor-positive breast cancers generally have a better prognosis than hormone receptor-negative cancers. They tend to grow more slowly and are less aggressive. Additionally, hormone receptor-positive cancers are more likely to respond to hormone therapies, which can reduce the risk of recurrence and improve long-term outcomes.
ER and PR status is assessed through a test called immunohistochemistry (IHC), which is performed on a sample of the tumour tissue obtained from a biopsy or surgery. The test measures the presence of these hormone receptors inside the cancer cells.
Here’s how the results are typically reported:
In pathology, a margin is the edge of a tissue that is cut when removing a tumour from the body. The margins described in a pathology report are very important because they tell you if the entire tumour was removed or if some of the tumour was left behind. The margin status will determine what (if any) additional treatment you may require.
Most pathology reports only describe margins after a surgical procedure called an excision or resection has been performed to remove the entire tumour. For this reason, margins are not usually described after a procedure called a biopsy is performed to remove only part of the tumour. The number of margins described in a pathology report depends on the types of tissues removed and the tumour’s location. The size of the margin (the amount of normal tissue between the tumour and the cut edge) depends on the type of tumour being removed and the location of the tumour.
Pathologists carefully examine the margins to look for tumour cells at the cut edge of the tissue. If tumour cells are seen at the cut edge of the tissue, the margin will be described as positive. If no tumour cells are seen at the cut edge of the tissue, a margin will be described as negative. Even if all of the margins are negative, some pathology reports will also measure the closest tumour cells to the cut edge of the tissue.
A positive (or very close) margin is important because it means that tumour cells may have been left behind in your body when the tumour was surgically removed. For this reason, patients with a positive margin may be offered another surgery to remove the rest of the tumour or radiation therapy to the area of the body with the positive margin.
Because ductal carcinoma in situ is a non-invasive form of cancer and is always given the pathologic tumour stage pTis.
Doctors wrote this article to help you read and understand your pathology report. Contact us with any questions about this article or your pathology report. Read this article for a more general introduction to the parts of a typical pathology report.