Understanding your pathology report

The pathologist will compile a report of the findings and your breast specialist will discuss the results with you. Your pathology report will contain the following information:

Gross description (macro)

This is a description and measurement of the removed part of your breast (surgical specimen) as seen without a microscope.

Microscopic description (micro)

This is a description and measurement of the surgical specimen when viewed under the microscope. This will include:

• The type of breast cancer
  This will tell you whether it is invasive/infiltrating (has spread outside the breast ducts into normal breast tissue) or in-situ (still contained within the breast ducts). Invasive cancer can be classified as ductal, lobular or another special type. In-situ disease is called ductal carcinoma in-situ (DCIS).

• The size of the tumour
  This is expressed in millimetres.

• The number of tumours in the breast. If there is more than one tumour in the breast it will be described as either multi-focal (tumours confined to one quarter of the breast) or multicentric (tumours in different quarters of the breast).

• The grade of the cancer

This tells you how abnormal the cells are and how rapidly they are dividing. This is usually expressed as:

• Grade 1 (low grade, well differentiated, slow growing),
• Grade 2 (intermediate grade, moderately differentiated, faster growing)
• or Grade 3 (high grade, poorly differentiated/undifferentiated, fast growing)

DCIS is classified separately, as either low, intermediate or high grade.

Lymph node status

This will tell you how many lymph nodes were removed during surgery and whether any of them contain cancer cells.

Receptors

Regardless of the type of breast cancer, tests will be performed on the tumour to establish whether the cells are under the influence of the female hormones oestrogen and progesterone, or of HER2 (Human Epidermal growth factor Receptor 2).

ER & PR (oestrogen and progesterone receptors)

These receptors indicate whether the cancer is likely to respond to hormone blocking therapy. Two-thirds of breast cancers have hormone receptor proteins on their surface which bind to oestrogen and/or progesterone, receiving signals that help them to grow. If these are present the cancer cells are described as ER and/or PR positive, indicating that hormone-blocking therapy may be effective in reducing cancer recurrence.

Read more about hormone-blocking therapy

HER2 receptor status
HER2 receptors or proteins are present in all breast cells and they help control how healthy breasts grow. In approximately 25% of breast cancers there are too many of these proteins, which contribute to the breast cancer cells growing and dividing more rapidly. These are called HER2-positive cancers, and they have an aggressive growth pattern and a higher risk of recurrence compared to HER2-negative cancers. An antibody treatment called Herceptin has been developed to treat early HER2-positive breast cancer.

Breast cancers are all tested for HER2 expression using immunohistochemistry (IHC). This is a process that uses antibodies to detect certain proteins within the sample of tissue. The results of this test will be reported as either:

• 0 (HER2-negative)
• 1+ (HER2-negative)
• 2+ (equivocal or borderline)
• 3+ (HER2-positive)

0 and 1+ are clearly negative and 3+ is clearly positive – in these cases, further testing is not required.

If the IHC test is 2+ (equivocal or uncertain) further testing will be done using FISH (Fluorescence In Situ Hybridisation). This test looks at whether the cells contain too many copies of the HER2 gene. FISH results are either positive (extra copies of the HER2 gene) or negative (normal number of copies).

Some breast cancers may change their ER, PR and/or HER2 status over time, so any recurrences of the cancer will be retested.

Lymphovascular invasion/vascular space invasion

The presence of lymphovascular invasion indicates that cancer cells were found in blood or lymphatic vessels surrounding the tumour.

Surgical margins
In the surgical specimen,the small amount of tissue surrounding the cancer needs to be clear of cancer cells to ensure the whole tumour has been taken out. If any edge of the specimen contains cancer cells, further surgery may be required. Surgical margins will be reported as negative (clear margins), close (cancer cells are close to the edge(s) of the specimen) or positive (cancer cells are present at the edge(s) of the specimen).

Ki-67
This is an immunohistochemical test that can be performed in the laboratory along with other tests on your tumour. The Ki-67 protein is detected in cells that are actively dividing, so it is a marker of proliferation (cell growth and division). The staining pattern of the Ki-67 protein is assessed and given a score. A Ki-67 level of less than 10% is considered low, 10-20% borderline and over 20% is high. There are problems in laboratory variations, interpretation and usefulness, so this test is not routinely used in many centres. However, your specialist team may request it to be done, if they feel it would provide useful information in addition to the other results on your pathology report.

Taking all of this information into account, you will be advised if there is a need for more local treatment (e.g. further surgery and/or radiation therapy) or whole body treatment such as chemotherapy, hormone-blocking therapy or targeted biological therapy. These decisions will be made in consultation with you, your family and your specialists.

What does my pathology report mean?