Types & Sub-Types

It’s important to know your breast cancer type and sub-type because it can make a difference in the selection of treatments that are recommended.  Your cancer can have more than one sub-type. Sub-types can also change when cancer recurs (comes back following a period where it could not be detected) or spreads. This happens in up to 20 to 30% of cases.

Types of Breast Cancer

Ductal Carcinoma in Situ (DCIS) refers to abnormal cells found within the milk ducts that are considered non-invasive as the cells have not spread from the ducts to the surrounding breast tissue. This is an early form of cancer that in some cases could potentially become invasive and spread to other tissues.

Lobular Carcinoma in Situ (LCIS) refers to abnormal cells found within the lobules, the milk-producing glands, of the breast.  While it is uncommon for LCIS to develop into invasive cancer, this condition is linked to an increased risk of developing invasive breast cancer later in life.

Invasive ductal carcinoma is a cancer that begins in the ducts (passages that carry milk from the glands to the nipple) and has spread to the surrounding breast tissue.

Secretory Breast Carcinoma is a cancer that occurs due to an over secretion of mucin in the tumor. It is considered a subtype of invasive ductal carcinoma but is prone to metastasis and local recurrence. It is a slow-growing cancer that is best to treat aggressively and it represents less than 0.1% of all cases of invasive breast cancer. Possible treatment options include chemotherapy, radiation and mastectomy; treatment decisions are made on an individual basis due to the rarity of this subtype of breast cancer.

Invasive lobular carcinoma is a cancer that starts in the lobules (groups of glands that create milk) and has spread to breast tissue nearby.

Lobular Breast Cancer Alliance provides more information on invasive lobular carcinoma (ILC) and Living with Lobular Breast Cancer in Canada  is a private Facebook group that shars research and resources for those with ILC.

Metaplastic breast cancer is a rare type of cancer that begins as one type of cancer cell that changes into another type of cancer cell. Less than one percent of breast cancers are metaplastic and it can be treated with surgery, radiation, and chemotherapy.

Inflammatory breast cancer is a rare form of breast cancer that causes the breast to appear red, swollen and tender, often resembling an infection. It is an aggressive, locally advanced (breast cancer that has spread to the nearby tissues and/or lymph nodes, but not to the other organs) form of cancer that blocks the lymph vessels in the skin of the breast. Symptoms of inflammatory breast cancer can develop very quickly and are often similar to other disorders. If you notice rapid swelling, skin changes or notice unusual sensations including pain or itching speak to your physician.

Metastatic breast cancer, also known as advanced, or Stage IV breast cancer, is the spread of cancerous cell growth to areas of the body other than the breast where the cancer first formed. Close to 1,200 Canadian women will receive an initial diagnosis of metastatic breast cancer each year. Some women who had an initial diagnosis of an earlier stage of breast cancer will go on to develop metastatic breast cancer.  The risk of this is highly individual, and depends on various clinical and pathological features of the initial tumour.  Unfortunately, at this time there are no current statistics in Canada to indicate how many people progress from early stage to metastatic.

Metastasis, or the spreading of cancer to a distant location in the body, can happen before or after treatment of the cancer in the breast.  It may be the result of a recurrence of breast cancer (breast cancer that returns following a period where it could not be detected). Though breast cancer cells can spread to almost any part of the body, they most commonly spread to the bones. Other common sites include the lungs, liver, brain and skin. It is this distant site of breast cancer that is called a metastasis.

Visit our Living with Metastatic Breast Cancer section to better understand your diagnosis. Our recently updated and re-written Metastatic Breast Cancer Handbook: A guide for individuals living with stage IV breast cancer offers a deeper look at how metastatic breast cancer affects your daily life and provides ways to help manage the changes that it brings.

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