Virtual Medical Centre

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
  • Grading of pathology results for breast cancer
  • Invasive vs non-invasive (in situ) 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 scans (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.