Diagnosis and staging

If screening tests have shown that you might have breast cancer, you will need to get diagnostic tests to tell you whether it’s actually cancer. Typically your GP will refer you.

Most things that show up in screening (including up to 90 percent of lumps in the breast) are not cancer. However, diagnostic tests are the only way to be sure whether something unusual in the breast is benign (not cancerous) or malignant (cancerous).

There are two types of diagnostic test:

  • Imaging. Creating a image of the interior of the breast. For example, mammography, or breast ultrasound.
  • Biopsy. Removal of a sample of cells from the breast for analysis in a lab.

Diagnostic imaging

These are tests that create an image of your breast. They are usually the first tests the doctor will use if a screening test, such as a screening mammogram or a breast exam, shows signs of cancer.

Diagnostic mammogram

If something unusual shows up on a screening mammogram, or if something about your breast changes (see Symptoms of breast cancer), your doctor may refer you for a diagnostic mammogram.

The difference between screening and diagnostic mammography is this:

  • Screening mammography looks for signs of possible cancer.
  • Diagnostic mammography checks whether a sign of cancer is actually benign (not cancer), or whether it needs to be investigated further.

A diagnostic mammogram uses a low-dose X-ray to get a detailed picture of the breasts. It is more thorough and takes a little longer than a screening mammogram. It provides more detailed images and views of the breast taken from different angles.

Diagnostic mammography is usually done on both breasts so that doctors can compare the breast tissue.

If you have breast implants, let the person conducting the mammogram know. They may take more X-ray pictures in order to ensure that the mammogram shows as much of your breast tissue as possible.

During pregnancy

Mammograms during pregnancy are generally regarded as safe. The amount of radiation is small, and a lead shield over the abdomen is used to shield the fetus from the radiation. That said, many pregnant women choose to postpone their mammogram until after their pregnancy is finished, so that they do not have to worry about any potential harm to the fetus. Radiation can certainly cause harm to a fetus, but it’s not clear unclear whether mammograms in particular are a risk, because the amount of radiation that the fetus receives is so small. If you are pregnant and you need a diagnostic mammogram, talk to your doctor about what diagnostic method is best for you. An ultrasound of the breast is often used as a safe alternative to a mammogram for pregnant women.

Learn more about mammograms (Canadian Cancer Society).


Ultrasound uses high-frequency sound waves to create an image of the internal structure of an organ. It is also called sonography.

Breast ultrasound is often used to diagnose a lump or abnormal area in the breast that was found with a mammogram or a physical breast examination. to determine if the lump is a solid tumour or a fluid-filled cyst. Ultrasounds are also used to visually guide a health care practitioner for other procedures such as biopsies.

A gel is spread on your skin in the area being examined and a small handheld instrument is passed over the area to form an image called a sonogram. The device sends out harmless sound waves and the reflected sound waves form a picture of the internal structure of your breast.

There is no radiation involved, which makes it the preferred method of diagnostic imaging for pregnant women (Canadian Cancer Society).

Women with highly dense breasts are often screened with ultrasound because mammograms of women with dense breast tissue tend to be hard to interpret.

The test can be performed in a doctor’s office, a clinic, or in a hospital as an outpatient procedure. The test usually takes 15 to 30 minutes, but may take longer. In general, after having a breast ultrasound, you can go back to your daily activities right away, as no anesthesia is required and the test causes no side effects or pain.

For more information, see Breast Ultrasound (RadiologyInfo.org).


MRIs are not routinely used to diagnose breast cancer, but is often used as an alternative device if results from a diagnostic mammogram and/or ultrasound are unclear, or the extent of breast cancer in the breast tissue, or to assess the type of breast cancer. Chiefly used to detect metastases and help in selecting a treatment, this technique can be an important complement to mammography as a screening tool in certain groups of women, particularly those with a BRCA gene mutation.

For more information about breast imaging techniques, watch this video: Comparing MRI, Mammography and Ultrasound in Breast Screening.


Biopsy means removing a small sample of breast tissue to be examined in a lab for signs of cancer. It is typically the only way to tell for certain whether a lump in the breast is cancer or not. If diagnostic imaging does not rule out the possibility of cancer, the next step is a biopsy.

The three main types of biopsy are fine needle aspiration biopsy (FNAB), core biopsy, and surgical biopsy.

Fine needle aspiration biopsy (FNAB)

A very thin needle is inserted into the lump to remove a small sample. No incision (cut) is necessary. If the lump is easy to find, this procedure may be done in a doctor’s office; in other cases, an ultrasound, mammogram, or MRI may be used to guide the needle. A fine needle aspiration biopsy may be done to help see whether the lump is a cyst (a fluid-filled sac) or a tumour.

Core biopsy

A large needle is guided into a part of the breast to remove a small cylinder of tissue (also called a core). No incision is necessary. Usually an ultrasound, mammogram, or MRI of the breast is used to help guide the needle.

Surgical biopsy

A surgeon removes part or all of a lump or suspicious area through an incision into the breast.

There are two types of surgical biopsies:

  • Incisional biopsy: a small part of the lump is removed.
  • Excisional biopsy: the entire lump is removed.

In some cases, if the breast lump is very small and deep and is difficult to locate, the wire localization technique may be used during surgery. With this technique, a special wire is placed into the lump under X-ray guidance. The surgeon then follows this wire to help locate the breast lump.

Pathology report, staging and grading

During a biopsy, tissues or cells are removed from the body so they can be tested in a laboratory. Once the health care provider receives the results, a preliminary pathology report is compiled. This information will confirm whether or not cancer cells are present in the sample and will determine which treatment method is best suited for the patient and their unique needs.

What is a pathology report and why is it important?

Pathology reports provide important information about your breast cancer. When breast tissue is removed, a pathologist, a doctor who specializes in examining tissue and diagnosing disease, examines it under a microscope. A preliminary pathology report is prepared after a breast biopsy. A more detailed report is prepared after your breast surgery (lumpectomy or mastectomy). Only after gathering all of the details in your pathology report can your surgeon determine the next steps in your treatment.

What kind of information is contained in a pathology report?

The report describes the characteristics of your tumour, such as:

Size of tumour

The size of the tumour is one of the factors that determines the stage of the breast cancer. Size doesn’t tell the whole story – all of the cancer’s characteristics are important. A small cancer can be very fast-growing while a larger cancer may be slow-growing, or it could be the other way around. Doctors measure cancer in centimetres.

Lymph node status

The lymphatic system is a network of vessels throughout the body that drain fluid from tissues. Bacteria and other microbes, including cancer cells, are picked up in the lymphatic fluid and trapped inside lymph nodes, where they can be attacked and destroyed by white blood cells. The lymph nodes act as filters along the lymph fluid channel. The fluid leaves the breast and eventually goes back in the bloodstream. The lymph nodes try to catch and trap cancer cells before they reach other parts of the body. Having cancer cells in the lymph nodes under your arm is associated with an increased risk of the cancer spreading, which leads to metastatic breast cancer.

Stage of the cancer

Staging consists of clinical examinations and tests done to determine the extent, or stage, of the cancer. Staging considers the size of the cancer and whether it has spread to nearby breast tissue or other parts of the body. Staging is important because it will help determine the best treatment plan. The pathology report that is prepared after your surgery will provide information necessary to determine the stage of your breast cancer. Sometimes additional tests may be required.

Grade of the cancer

Breast cancer is also classified as a grade. Grade indicates how aggressive the cancer is likely to be, meaning how fast it will grow and spread. The grade is determined by examining the appearance and behaviour of cancer cells under a microscope. The more cancer cells look and behave like normal cells, the slower the cancer is likely to grow and spread, and the lower the grade assigned.


Differentiation refers to how cancer cells look and function compared to normal cells. A tumour’s level of differentiation can vary with time and can be described in degrees.

Well-differentiated cancer cells look and behave like the normal cells in the tissue they started to grow in. Tumours that contain well-differentiated cancer cells tend to be slow growing and less aggressive.

Undifferentiated or poorly differentiated cancer cells look and behave quite differently from normal cells in the tissue they started to grow in. They look immature or undeveloped and often do not resemble the tissue of origin at all. Tumours that contain undifferentiated or poorly differentiated cancer cells are more aggressive. They tend to grow quicker, spread more often and have a worse prognosis than tumours with well-differentiated cancer cells.

Moderately differentiated cancer cells look and behave somewhere between well-differentiated and undifferentiated cancer cells. Most types of cancer have moderately differentiated cancer cells.

Invasive or non-invasive

Breast cancer usually begins either in the cells of the lobules, which are milk-producing glands, or the ducts, the passages that drain milk from the lobules to the nipple. The pathology report will tell you whether or not the cancer has spread outside the milk ducts or lobules of the breast where it started (breastcancer.org).

Non-invasive breast cancer (or “in situ” cancer) refers to a type of cancer where the breast cancer cells have not spread beyond their originated location – the cancer cells have not “invaded” the surrounding breast tissue. Often in situ breast cancer is referred to as a pre-cancerous condition, as it can develop into invasive cancers.

Invasive breast cancer (sometimes called infiltrating breast cancer) refers to a type of cancer where the breast cancer cells have spread beyond their originated location – the cancer cells have “invaded” the surrounding breast tissue and can travel to other parts of the body, such as the lymph nodes.

Hormone receptor status

Some breast cancer cells have receptors into which the female hormone molecules (estrogen and progesterone) fit like a lock and key. These are known as hormone receptor positive (HR+) cancers. If these receptors are present, hormones will encourage the cancer to grow. It also means they are more likely to respond to hormone therapy for treatment. HR+ cancers can be estrogen receptor positive (ER+), progesterone receptor positive (PR+), or both.

You will see the results of your hormone receptor in one of three ways:

1. The number of cells that have receptors out of 100 cells tested. You will see a number between 0 per cent (none have receptors) and 100 per cent (all have receptors).

2. A number between 0 and 3. 0 (no receptors) 1+ (a small number of cells have receptors) 2+ (a medium number of cells have receptors) 3+ (a large number of cells have receptors)

3. The word “positive” or “negative.”

Source: Your Guide to the Breast Cancer Pathology Report (BreastCancer.org).

HER2 status

Your pathology report usually includes the cancer’s HER2 Status. HER2-positive breast cancer is a breast cancer that tests positive for the protein called human epidermal growth factor receptor 2 (HER2). These proteins are receptors on breast cells, which promotes the growth of cancer cells. HER2-positive breast cancers often contain lower levels of estrogen and progesterone receptors than HER2-negative tumours. Therefore, women with HER2-positive breast cancer may benefit less from certain types of hormonal therapy.

Read more about HER2 status (BreastCancer.org).

Margin status

When surgery is done to remove the whole cancer, the surgeon tries to take out all of the cancer with an extra area, or margin of normal tissue surrounding the tumour. The pathologist measures the distance between the cancer cells and the margin. Margins around a cancer are described in three ways:

  • Negative: No cancer cells can be seen at the outer edge. Usually, no more surgery is needed.
  • Positive: Cancer cells come right out to the edge of the tissue. More surgery is usually needed to remove any remaining cancer cells.
  • Close: Cancer cells are close to the edge of the tissue, but not right at the edge. More surgery may be needed.

Read more about margin status (BreastCancer.org).


You may see these descriptions of the type of cancer cells in your report (click on each for more information)

  • Ductal Carcinoma In-Situ (DCIS)
  • Lobular Carcinoma in Situ (LCIS)
  • Infiltrating Ductal Carcinoma (IDC)
  • Medullary Carcinoma
  • Infiltrating Lobular Carcinoma (ILC)
  • Tubular Carcinoma
  • Mucinous Carcinoma (Colloid)
  • Paget’s Disease
  • Inflammatory Breast Cancer (IBC)


Breast cancer can be classified in the following stages:

STAGE 0: This is non-invasive DCIS (ductal carcinoma in situ); the cancer stays within the ducts of the breast. Some consider this to be pre-cancer.

STAGE I: This is early invasive breast cancer. The tumour is 2 cm or less and cancer has not spread to lymph nodes.

STAGE II: This is still considered early invasive breast cancer, but the tumour is larger (2 – 5 cm) and/or the cancer has spread to a few nearby lymph nodes.

STAGE III: This is locally advanced breast cancer. The tumour is either larger than 5 cm, or extends to the chest wall or involves the skin of the breast, or has spread to many nearby lymph nodes.

STAGE IV: This is metastatic or advanced breast cancer. The cancer has spread to other parts of the body, such as bone, liver, lungs, or brain.