Understanding my breast cancer

When you find out you have breast cancer many new terms and treatments are discussed, and it can be very overwhelming to know what it all means.

Below you will find information specific to your breast cancer based on the attributes you selected at the beginning of this tool. If you do not know your stage, type, or sub-type the information below will give you information about all breast cancer stages, types or sub-types.

Regardless of the information outlined below, it is always important to remember that the most accurate and up-to-date information should always come from your doctor.

The more you understand about your diagnosis the more you can participate in your care. But sometimes too much information can make feelings of anxiety and uncertainty worse. You know best how much information is too much for you to digest. If ever you are feeling like the information you are reading, here or elsewhere, is making you feel overwhelmed, take a step back and take a break.

*Remember: Not all experiences may follow this exact path and you may or may not have all the tests or treatments we outline within. We hope this pathway will give you a general understanding of the process and possible standard categories. We encourage you to always consult your doctor for the most accurate information and timelines specific to your circumstances.

What is breast cancer?

Breast cancer occurs when breast cells begin to grow and divide at an uncontrolled pace. Typically, breast cancer begins either in the cells of the ducts (the channels that carry milk from the glands to the nipple) or the lobules (the group of glands that create milk). Breast cancer that starts in the ducts is called ductal carcinoma, while breast cancer that begins in the lobules is referred to as lobular carcinoma.

There are 4 main characteristics of breast cancer that determine your treatment:

• Stage
• Type
• Sub-type
• Grade

Stage

Staging breast cancer can be very complex. Overall, there are 5 stages ranging from stage 0 to stage IV. Staging systems classify breast cancers according to the size of the tumour and whether or not it has spread to nearby tissue, lymph nodes or other areas/organs in the body. The common staging system used by doctors in Canada is known as the TNM System because it classifies tumours by:

• Tumour size (T)
• Lymph nodes involved (N), and
• Metastases (spread) (M)

Stage 0: This stage is a non-invasive form of breast cancer known as ductal carcinoma in situ (DCIS) or lobular carcinoma in situ (LCIS). It is also commonly referred to as pre-invasive cancer.

DCIS is a cancer that forms within the ducts but has not spread through the walls of the ducts. It is treated similarly to invasive breast cancer because it is possible for the cancer cells to become invasive. This form of breast cancer is highly treatable and curable.

LCIS is an abnormal growth of cells within the lobules but is generally not considered cancer. If you have been diagnosed with LCIS you are at an increased risk of developing breast cancer. Increased screening and surveillance are the most common forms of treatment for LCIS.

The TNM code associated with stage 0 breast cancer is: Tis N0 M0

Tis = Carcinoma in situ
N0 = No cancer in lymph nodes
M0 = No spread organs outside the breast

Stage I: This early stage of breast cancer refers to cancers that are small in size – 2 cm or smaller. Most commonly, the lymph nodes show no signs of cancer (stage IA). If cancer cells are present, it is no larger than 2.0mm (stage IB). This refers to the “anatomic stage”. Sometimes larger tumours or those involving lymph nodes can still have their stage “adjusted” to stage I if they have otherwise very good biological features.

The TNM code associated with stage IA breast cancer is: T1 N0 M0

T1 = Tumour is 2 cm or less
N0 = No cancer in lymph nodes
M0 = No spread organs outside the breast

The TNM codes associated with stage IB breast cancer are:

Stage II: This stage of breast cancer is still considered early stage and refers to invasive cancers 2 cm (and less than 5 cm) or involving 1 to 4 lymph nodes. This refers to the “anatomic stage”. Sometimes larger tumours or those involving lymph nodes can still have their stage adjusted to stage I if they have otherwise very good biological features. 

Stage IIA breast cancer refers to cancers that are no more than 2 cm, and:

• Has spread to 1 to 3 axillary lymph nodes (lymph nodes in the armpit closest to the breast)
• Has spread to internal mammary lymph nodes (the lymph nodes that carry breast lymphatic drainage)
• The tumour may be more than 2 cm but no more than 5 cm and has not spread to the lymph nodes

The TNM codes associated with stage IIA breast cancer are:

Stage IIB breast cancer refers to cancers that are larger than 2 cm but no more than 5 cm and have spread to 1-3 axillary lymph nodes and/or internal mammary lymph nodes. Stage IIB can also refer to cancers that are larger than 5 cm but have not spread to lymph nodes.

The TNM codes associated with stage IIB breast cancer are:

Stage III: This stage of invasive cancer means that the cancer has spread locally to nearby lymph nodes or the chest wall (the skin, fat or muscles in your chest). Commonly, stage III breast cancers are either greater than 5 cm or involve more than 4 lymph nodes. Sometimes larger tumours or those involving lymph nodes can still have their stage adjusted to a lower stage if they have otherwise very good biological features.

This stage of breast cancer is considered to be locally advanced but treatable. Stage III is broken into three sub-groups:

Stage IIIA breast cancer refers to cancers that are:

• The tumour is no more than 5 cm and has spread to 4 to 9 axillary nodes (lymph nodes in the armpit closest to the breast) or has enlarged internal mammary nodes (the lymph nodes that carry breast lymphatic drainage)
• The tumour is larger than 5 cm and has spread to 1 to 9 axillary nodes and/or internal mammary nodes

The TNM codes associated with stage IIIA breast cancer are:

Stage IIIB breast cancer refers to cancers that have spread to the chest wall or the skin. It may or may not have spread into lymph nodes but has not spread to organs outside of the breast. Stage IIIB can also refer to inflammatory breast cancer, a rare form of breast cancer that causes the breast to appear red, swollen and tender, often resembling an infection. (For more information and resources on rare breast cancer types, visit Community Resources in Managing the Impact of Breast Cancer section.)

The TNM codes associated with stage IIIB breast cancer are:

Stage IIIC breast cancer can be any size and has spread to either:

• 10 or more axillary lymph nodes or to lymph nodes under the collarbone
• 3 or more axillary lymph nodes and internal mammary lymph nodes
• Lymph nodes above the collarbone

The TNM code associated with stage IIIC breast cancer is: T(any) N3 M0

T(any) = No tumour or tumour of any size
N3 = Cancer in at least 10 axillary nodes or nodes under the collarbone; in internal mammary nodes on the same side plus at least one axillary node; in more than 3 axillary nodes plus internal mammary nodes; or in nodes above the collarbone
M0 = No spread to organs outside the breast

Stage IV: Stage IV breast cancer is also commonly known as metastatic breast cancer (mBC). This stage of breast cancer means that the cancer has spread beyond the breast into other organs in the body, most commonly the bones, lungs, liver or brain. Cancer cells that have spread beyond the breast are still considered breast cancer and will be treated with breast cancer treatments.

Metastatic breast cancer can be de novo, meaning it is your first breast cancer diagnosis, or recurrent, meaning your previously treated breast cancer has returned elsewhere in your body and is now stage IV.

mBC is different from early-stage breast cancer because it means you will be living with cancer for the rest of your life. This means that you will always be treated and monitored by your healthcare team. While early-stage breast cancer is treated with the goal to remove the cancer entirely, metastatic breast cancer at present is not curable. Instead, the goal of treatment, in most cases, is to manage the disease by slowing the growth of the cancer cells, managing symptoms and preventing the disease from continuing to spread so that you can continue to live a full and meaningful life.

In some circumstances, people diagnosed with oligometastatic breast cancer may be able to treat their breast cancer in a similar way as early-stage breast cancer. Oligometastatic means that the cancer has spread to a few areas and the tumours are small or there are very few of them. In these cases, surgery to remove the tumour completely may be an option.

The TNM code associated with stage IV breast cancer is: T(any) N(any) M1

T(any) = No tumour or tumour of any size
N(any) = None or any cancer in lymph nodes
M1 = Spread to organs away from the breast area

Type

Breast cancer types are classified by a couple of different features. Your breast cancer can be invasive or non-invasive and can start in the ducts or the lobules.

Non-invasive, also known as in situ, cancer cells have not spread outside the tissue where the cancer was first detected in the breast.

Invasive cancer cells have spread into the surrounding tissue of the breast.

The most common types of breast cancer are:

• Ductal carcinoma in situ (stage 0)
• Invasive ductal carcinoma
• Invasive lobular carcinoma

In Situ Breast Cancer

Ductal carcinoma in situ (DCIS), also considered stage 0 breast cancer, originates in the lining of the breast milk ducts and does not spread to the surrounding breast tissue. DCIS is the most common non-invasive breast cancer type but is a treatable early-stage cancer.

Lobular carcinoma in situ (LCIS), also called lobular neoplasia (group of abnormal cells), is characterized as a buildup of abnormal cell growth in the lobules that has not spread to surrounding breast tissues but can develop in different lobules in the breasts. Even though the name carcinoma suggests cancer, LCIS is not considered a cancer. Alternatively, LCIS is a breast condition with a small increased risk of developing invasive breast cancer.

Invasive Ductal Carcinoma

Invasive ductal carcinoma (IDC), also called infiltrating ductal carcinoma, originates in the breast ducts and spreads through the duct wall into surrounding breast tissue. IDC is the most common invasive breast cancer type.

Invasive Lobular Carcinoma

Invasive lobular carcinoma (ILC), also known as infiltrating lobular carcinoma, is an invasive breast cancer originating in the lobules of the breast that spreads into surrounding breast tissue. Like other invasive breast cancer, ILC can metastasize to lymph nodes and spread to other areas of the body. ILC can occur in different lobules in the breast and is likely to occur in both breasts.

Diagnosing lobular breast cancer can be challenging because the cells do not often form a lump. Mammograms often underestimate the true size of the cancer. Biopsy and other imaging such as ultrasound or MRI are the best forms of diagnostic tools for diagnosing ILC. Once diagnosed, treatment for ILC is similar to invasive ductal carcinoma.

Rare Breast Cancer Types

Other rare types of breast cancer include:

• Inflammatory breast cancer: a rare and aggressive presentation of invasive ductal carcinoma that makes up about 1-5% of all breast cancers. IBC presents with symptoms of inflammation (redness and warm skin) of the breasts, changes of breast colour (red/purple like a bruise) on a third of the breast, dimples (it may look like the peel of an orange) and pain and swelling of the breast. It may resemble a breast infection but will not respond to antibiotic treatments.
• Metaplastic breast cancer: a rare type of cancer that begins as one type of cancer cell that changes into another type of cancer cell.

For more information and resources on rare breast cancer types, visit Additional Treatment Resources in the Making Treatment Decisions section.

Sub-type

Breast cancer sub-type is an important characteristic of your breast cancer because it can help determine what treatments are right for you. There are two main characteristics that will classify your breast cancer sub-type:

• Hormone receptor status (ER or PR): Hormones estrogen and progesterone encourage the growth of normal breast cells by stimulating their estrogen receptors (ER) and progesterone receptors (PR). If a breast cancer is found to have ERs or PRs on its surfaces, that means the cancer relies primarily on those hormones to survive. A tumour may have any combination of ER or PR. Any presence of estrogen or progesterone receptors makes the breast cancer HR positive (+)
• HER2 status (Human epidermal growth factor receptor 2): Growth factors are substances that circulate in the blood and can attach to receptors that sit on the surface of a cell, setting off a chain of reactions inside the cell that ends up stimulating the cell’s growth. Normal cells in the breast have a receptor on their surfaces called human epidermal growth factor receptor 2 (HER2), which acts as a docking station for certain growth factors in the blood. A gene that is called HER2, Her2/neu, or ErbB2 controls the amount of HER2 receptors on the cell surface. Normal cells contain two copies of this gene. Breast cancers that contain more than 2 copies of the HER2 gene, and therefore produce too much of the HER2 receptor protein (also known as overexpressing HER2) are considered to be HER2 positive (+).

Having different combinations of these receptors will classify your breast cancer sub-type. It is crucial to know what your breast cancer sub-type is as it will greatly impact your treatment options.

HR positive; HER2 negative

Breast cancers considered to be HR positive and HER2 negative are also called Luminal A breast cancers. This sub-type typically develops slower and tends to have a good prognosis. If your breast cancer is HR+, HER2-, you may benefit from treatments that specifically target hormone receptors, estrogen, and progesterone. These treatments include endocrine therapy, also known as hormonal therapy and HR+ targeted therapies.

HR positive, HER2 positive

Breast cancers that are classified as being both HR positive and HER2 positive can benefit from treatments that specifically target HR positive breast cancers and HER2 positive breast cancers. A person can have any combination of ER/PR hormones and also be HER2 positive.

Luminal B breast cancers are ER positive and PR low-positive or PR negative and are also HER2 positive. HER2 overexpressing breast cancer can be ER positive or negative and/or PR positive or negative and HER2 positive. If a person is both ER and PR positive while also being HER2 positive, this can often be called “triple positive”.

Luminal B breast cancers can develop faster than luminal A and may have a poorer prognosis. This is due to a high tumour grade and size and is more likely to have lymph node involvement.

Treatment for HR positive, HER2 positive breast cancers can include endocrine therapy, HER2 targeted therapies, HR+ targeted therapies and chemotherapy.

HER2 positive, HR negative

Breast cancers that are classified as being HER2 positive, but HR negative can benefit from treatments that specifically target the HER2 protein and will not benefit from hormonal therapies or HR targeted treatments. Chemotherapy is often added to most HER2 targeted therapies. 

Triple-Negative (HR negative, HER2 Negative)

Triple-negative breast cancer (TNBC) means that the cells do not contain hormone receptors (estrogen or progesterone), nor do they contain the HER2 protein. Triple-negative breast cancers test negative for all three, hence their name.

TNBC is commonly treated with the use of chemotherapy. There are new treatment options for individuals who are BRCA positive (the breast cancer gene mutation).