Breast Cancer: Types, Stages and Ways to Manage It
Broadly defined, “breast cancer” refers to cancerous cells originating in different parts of the breast growing out of control. The three primary parts of the breast are the lobules (glands that produce milk), ducts (tubes that carry milk to the nipple), and connective tissue (the fatty tissue that holds everything together) (2).
When breast cancer spreads to other areas of the body, it is said to have metastasized.
Save for skin cancer, breast cancer is the most common form of cancer affecting women. According to the American Cancer Society (ACS), the average overall risk for a woman in the United States to develop breast cancer at some point in her lifetime is 13%. Ahead of 2020, ACS estimated more than 276,000 new cases of invasive breast cancer and nearly 49,000 new cases of non-invasive breast cancer would be diagnosed through the year. More than 42,000 women die from breast cancer each year(3).
With this disease being so common, it is important to understand what breast cancer is, the different types, how it is diagnosed and treatment strategies.
Types of Breast Cancer
There are many different types of breast cancer, although they are generally described by two factors: where the cancer begins and whether or not the cancer has spread.
With respect to origin, the majority of breast cancers are “carcinomas,” meaning they start in the epithelial cells that line the tissues and organs throughout the body. Specifically, carcinomas in the breast are usually more specifically called “adenocarcinoma,” meaning they start in cells of the milk ducts or milk-producing glands (lobules)(1).
Then there are “in situ” and “invasive” breast cancers. In situ breast cancer is cancer in a milk duct that has not advanced into the rest of the breast tissue – also called ductal carcinoma in situ or “DCIS”. Invasive breast cancer is any type of breast cancer that has spread into the surrounding breast tissue. Invasive breast cancers are typically either invasive ductal carcinoma or invasive lobular carcinoma. About 70-80% of all breast cancers are classified as invasive ductal carcinoma (1).
Specific Types of Invasive Breast Cancer
Certain forms of invasive breast cancer have special features or progress in different ways that affect their treatment and outlook. While these cancers are less common, they tend to be more severe than other forms:
- Triple-negative breast cancer. An aggressive, difficult-to-treat form of invasive breast cancer. Account for 15% of all breast cancers.
- Inflammatory breast cancer. An uncommon form of invasive breast cancer that accounts for approximately 1% to 5% of all breast cancers.
Rare Breast Cancer Types
In rare cases, breast cancers can affect other types of cells in the breast tissue. These can require different treatment strategies (1):
- Paget disease of the breast. Cancer that starts in the ducts and spreads to the skin of the nipple and areola. Accounts for 1-3% of all breast cancer cases.
- Angiosarcoma. Cancer originating in the cells that line blood or lymph vessels. Accounts for less than 1% of all breast cancers.
- Phyllodes tumor. Tumors that form in the connective tissue of the breast. Phyllodes tumors are only cancerous in rare cases.
Stages of Breast Cancer
If you have received a breast cancer diagnosis, your doctor will then work “stage” your cancer – working to determine the extent of disease. A stage is assigned after the physical exam and initial results of a mammogram or other imaging test, but it may be adjusted after lab reports from biopsy or surgery. Staging is an important step toward determining the right treatment path (4).
Your doctor will use the “T-N-M Scale” to help determine the stage of breast cancer:
- T. Tumor size
- N. Involvement of nearby lymph nodes
- M. Metastasis – or whether the cancer has spread to other parts of the body
There are five stages of breast cancer – represented by 0 and the Roman numbers I – IV.
Stage 0
Very initial stages of breast cancer – either non-invasive or precancer. In Stage 0 cases there is no evidence that cancer cells or any abnormal cells have invaded nearby normal tissue.
Stage I
Earliest stages of invasive breast cancer – cancer cells have spread to nearby normal tissue but remain in a small, contained area. There are two subcategories within Stage I:
Stage 1A. A tumor in the breast up to 20 millimeters with no cancer in the lymph nodes.
Stage IB. Either:
- A tumor in the breast less than 20 millimeters and small clusters of cancer cells in the lymph nodes; or
- No tumor in the breast but small clusters of cancer cells in the lymph nodes.
Stage II
Cancer that remains in a limited region but has spread. Stage II is primarily assigned based on the extent to which the cancer has spread to the lymph nodes. There are two subcategories within Stage II:
Stage IIA. Cancer characterized as one of the following
- Cancer has spread to the lymph nodes under the arm, with or without a breast tumor (up to 20 millimeters)
- Cancer has not spread to the lymph nodes, but a breast tumor between 20–50 millimeters is present.
Stage IIB. Cancer characterized as one of the following:
- Cancer has spread to 1–3 nearby lymph nodes and there is a tumor between 20–50 millimeters in the breast
- Cancer has not spread to any lymph nodes but there is a tumor larger than 50 millimeters in the breast
Stage III
Cancer that has spread further into the breast or the tumor is bigger than those of earlier stages. Stage III is broken down in three subcategories:
Stage IIIA. Cancer characterized as one of the following:
- Cancer has spread to 4–9 nearby lymph nodes, with or without a breast tumor.
- Cancer has spread to 1–3 lymph nodes and a breast tumor bigger than 50 millimeters
Stage IIIB. Cancerous tumor has spread behind the breast to the chest wall. Additional characteristics of this stage include:
- Cancer has spread to the skin – causing inflammation or swelling
- Cancer has broken the skin – causing an open wound or ulcerated area
- Cancer has spread to up to nine lymph nodes under the arm or near the breastbone
Stage IIIC. No tumor or a tumor of any size in the breast with cancer spreading to the following locations:
- 10 or more underarm lymph nodes
- Lymph nodes close to the collarbone
- Combination of lymph nodes under the arm or near the breastbone
Stage IV
The most advanced form of the disease. At this stage cancer has spread to nearby lymph nodes as well as distant parts of the body – potentially affecting your organs or bones.
Overview
Your outlook after breast cancer depends on many things, including your cancer stage when you were diagnosed. Regardless of when you are diagnosed and at what stage you are at, there are typically a plethora of treatment options and paths you can go down.
