Pathology Testing for Breast Cancer
- Introduction to pathology testing for breast cancer
- What is involved in pathology testing for breast cancer?
- Interpretation of pathology results for breast cancer
- Factors involved in pathology testing for breast cancer
Introduction to pathology testing for breast cancer
Breast cancer is the most common cause of cancer-related death in women in Australia. The initial evaluation of a breast cancer usually involves a physical examination, mammogram, chest x-ray, and sometimes CT (specialized x-rays) or a bone scan. However, the final evaluation frequently depends upon the findings on pathology testing, which is the most accurate way to determine how far the tumour has spread.
Treatment and prognosis (disease outcome) depend on the stage of the cancer, which is based upon the size of the tumour, involvement of the skin, chest wall or local lymph nodes, and whether the cancer has spread to other parts of the body (also called metastasis).
What is involved in pathology testing for breast cancer?
In the patient with a suspicious abnormality on physical examination or mammogram, the best way to arrive at a diagnosis is through a biopsy. A biopsy can be performed in the form of percutaneous (through the skin) fine needle aspiration, percutaneous core needle biopsy, or excisional biopsy.
Fine needle aspiration is a simple and inexpensive procedure which uses a small needle to obtain sample cells or fluid from a mass.
Core needle biopsy, on the other hand, needs a larger needle, but is useful in differentiating non-invasive lesions from invasive lesions.
Excisional biopsy involves surgery and is carried out by the radiologist and the surgeon.
Interpretation of pathology results for breast cancer
When samples obtained from the procedure are sent to the laboratory, they are examined under the microscope and are placed through special tests in order to ascertain particular features.
The image below is an example of the appearance of cells under the microscope.
Grading of pathology results for breast cancer
Cancer cells are categorised using a grading system ranging from Grade 1 to Grade 3.
- Grade 1: In Grade 1, the cancer cells look like normal cells and are usually slow growing. This is referred to as “Low Grade” or “Well Differentiated”.
- Grade 2: In Grade 2, cancer cells do not resemble normal cells but instead appear to stick together and grow at a faster rate. This is called Intermediate/Moderate Grade or Moderately Differentiated.
- Grade 3: Grade 3 cancer cells have irregular shapes, stick together and are fast growing. This is called High Grade or Poorly Differentiated.
Invasive vs non-invasive (in-situ) cancer
Another important piece of information provided by pathology testing is whether the breast cancer is invasive or non-invasive. This affects the approach to treatment.
In invasive cancer, the cancer cells have spread beyond the original area of growth, i.e. beyond the milk ducts or lobules of the breast where it first started.
In non-invasive cancer, the cancer cells are contained within the original area of growth. This is sometimes called carcinoma in situ (‘in place’). The cancer cells stay within the milk ducts or milk lobules in the breast. They do not grow into or invade normal tissues within or beyond the breast.
- Ductal carcinoma in situ (DCIS): This is a type of very early breast cancer. The cells lining the milk ducts of the breast have overgrown and become cancerous, but do not have the ability to spread beyond the ducts.
- Lobular carcinoma in situ (LCIS): This is a tumour that is an overgrowth of cells that stay inside the lobules, the milk-making part of the breast. Again, LCIS is a very early form of cancer, sometimes called a pre-cancer.
- Invasive ductal carcinoma (IDC): This is a cancer that begins in the milk duct but grows into the surrounding normal tissue inside the breast. This is the most common kind of breast cancer.
- Invasive lobular carcinoma (ILC): This is a cancer that starts inside the milk-making glands (lobules), but grows into the surrounding normal tissue inside the breast.
The surgical treatment of non-invasive cancers is similar to that of invasive cancers, but systemic (bodywide) therapy after surgery (adjuvant therapy) is generally not recommended for in situ cancer. This is because the chance of recurrence for in situ cancer is much lower than that for cancer which has spread beyond the site of origin.
Factors involved in pathology testing for breast cancer
The size of the tumour is measured in centimetres. Tumour size is one of the factors to determine the stage of the cancer. The larger the cancer is, the higher the stage.
The margin of the cancer cells, which means how close to the outer edges of the tissue the cancer cells are found, can be described in three ways:
- Positive: This means that cancer cells come to the edge of the tissue. Further surgery is required.
- Negative/clean: No cancer cells are seen at the outer edge.
- Close margins: This is between positive and negative margins. Cancer cells are close to the edge of the tissue, but not right at the edge.
The breast has lymph nodes that filter along the lymph fluid channels that connect breast tissue to other parts of the body to remove waste products. Breast cancer cells, like the cells of other cancers, may have the potential to spread beyond their site of origin via the lymphatic channels. If this happens, cancer cells can be found in the ‘draining’ lymph nodes. The higher the number of cancerous lymph nodes, the greater the chance the cancer will return (recurrence) after treatment. In these cases, your doctor may recommend treatment to your whole body (systemic treatment), not just the breast area.
Lymph node involvement is either:
- Node negative (lymph nodes clear of cancer); or
- Node positive (lymph nodes contain cancer cells).
Hormone receptors on breast cells receive signals from hormones such as oestrogen and progesterone. These signals switch on growth in breast cells that have receptors. A cancer is called “oestrogen receptor-positive” if it has receptors for the hormone oestrogen. It is called “progesterone receptor-positive” if receptors for the hormone progesterone are present.
Breast cancers that are either oestrogen receptor-positive or progesterone receptor-positive, or both, tend to respond well to hormone therapy. In addition, patients with oestrogen- or progesterone-receptor positive breast cancers tend to do better than patients with receptor negative cancers.
HER-2 is a gene that helps control how cells grow, divide, and repair themselves. About 15-20% of breast cancers have too many copies of the HER-2 gene. The HER-2 gene directs the production of special proteins, called HER-2 receptors, in cancer cells. HER2-positive breast cancer is usually associated with more aggressive behaviour, with higher growth rate and proliferation rate and increased risk of invasion and spread (metastasis). But they do respond very well to treatment that works against HER-2.
Overall, the size and extent of the breast tumour, involvement of adjacent lymph nodes, and the presence or absence of spread to other organs are grouped together to form the “stage grouping” of a breast cancer, which ranges from stage I to IV. This staging system can help guide treatment decisions, such as whether adjuvant therapy with radiotherapy, chemotherapy or hormone therapy may be appropriate.
|For more information on breast cancer, types of breast cancer and its investigations and treatments, as well as some useful videos, see Breast Cancer.|
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