Normal Breast Tissue
A healthy female breast is made up of adipose tissue (fat cells) and lobes. The lobes contain many lobules. Lobules are responsible for milk production in lactating women. The lobes and lobules are connected via milk ducts (National Breast Cancer Foundation INC, 2019). All together, this system is responsible for transporting milk to the nipple. Breast cancer is known to originate in these structures. A healthy breast is also made up of fibrous connective tissue, lymph vessels, lymph nodes, and is well vascularized (National Breast Cancer Foundation INC, 2019). Well functioning lymph nodes filter out foreign cells and are key components in the immune system. The lymphatic drainage of the breast predominantly goes to the axillary lymph nodes. This is the most common site of lymphatic involvement with breast cancer (Tzou, n.d.).
Retrieved from https://www.nationalbreastcancer.org/breast-anatomy
Breast Cancer Pathophysiology
Breast cancer can stem from proliferative breast disease. This disease occurs when the ducts and/or lobes of the breast are enlarged. This enlargement, or hyperplasia, is often the first step in the development of cancer. In addition, small tumors will form inside of the milk ducts. These are known as intraductal papillomas (Shah, R. & Rosso, K., 2014).
Some breast cancers are inherited. These genetic forms of breast cancer account for 5%-10% of all breast cancer cases in the United States. The genes responsible for this form are named BRCA1 and BRCA2 and can be found on chromosomes 17 and 13 (McCance, K.L. & Huether, S.E., 2019). Normally, everyone has these genes. However, a mutation in one or both of these genes can be inherited and therefore increase the risk of breast cancer to whomever received the mutated gene (Susan G. Komen, 2018). The mutations of these genes are the most common causes of inherited breast cancer (McCance, K.L. & Huether, S.E., 2019).
Whether it’s from an inherited gene mutation or from other causes that are still unknown, breast cancer initially begins with cancerous cells forming inside the milk duct. Over time, the mass of cells form small tumors, and travel inside the duct. Eventually, they can pass through the ducts and invade the lobules and adipose tissue. Once the mass enters this invasive stage, it can spread into the lymphatic system, vasculature and overlying skin (Susan G. Komen, 2018). This process can take several years before a noticeable lump can be detected via physical exam.
McCance, K. L. & Huether, S. E. pg. 794
Diagnosis
A breast cancer diagnosis is dependent on many factors. Tumor size, invasive versus non-invasive, hormone receptor status, and microscopic description are all taken into account. Once a tumor is detected from a breast exam or mammogram, a biopsy sample is taken. The biopsy is closely examined under a microscope, using histology to determine the size, location and saturation of cancerous cells. Smaller tumors correlate with a better prognosis. In the past, the TNM system was commonly used as a diagnostic tool, investigating tumor size, lymph node status (number and location of lymph nodes involved), and metastases (Susan G. Komen, 2018). Today, classifying stages of breast cancer looks at characteristics beyond the TNM system. Such characteristics include tumor grade, hormone receptor status, HER2 (protein) status and more (Breastcancer.org, 2019). Below is a table that summarizes the new staging classification. For more detailed information, please click on the links provided.
| Stage 0 | Non-invasive (ductal carcinoma in-situ). Abnormal cells found in lining of milk duct. Highly treatable if found at this stage.
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| Stage 1A | Invasive. Tumor measures up to 2cm. No spreading outside of breast. Lymph nodes are not involved. Very treatable.
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| Stage 1B | Invasive. No tumor in breast. Small groups of cancer cells (smaller than 2mm) are found in the lymph nodes. Very treatable.
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| Stage 2A | Invasive. Cancer is larger than 2mm. Found in 1-3 axillary lymph nodes. Tumor measures 2cm or smaller and has spread to axillary lymph nodes.
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| Stage 2B | Invasive. Tumor is between 2 and 5 cm. Small groups of breast cancer cells found in lymph nodes.
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| Stage 3A | Invasive. Cancer has spread to 4-9 axillary nodes. Tumor is larger than 5 cm. The tumor is estrogen and progesterone receptor positive.
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| Stage 3B | Invasive. Tumor may be any size and has spread to chest wall or up to 9 axillary nodes. Estrogen and progesterone receptor positive.
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| Stage 3C | Invasive. Tumor may be any size. Spread to 10 or more axillary nodes. Estrogen and progesterone receptor positive.
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| Stage 4 or “metastatic” | Invasive breast cancer that has spread beyond the breast and lymph nodes to other organs of the body. Incurable. |
Summarized from https://www.breastcancer.org/symptoms/diagnosis/staging https://www.nationalbreastcancer.org/breast-cancer-stage-4
Diagnostic tools include mammograms, ultrasounds, MRI, biopsy and lab testing. Mammograms should be routine even when no symptoms of breast cancer are present. Ultrasound is ordered when a suspicious site has been detected from a self-breast exam or mammogram (National Breast Cancer Foundation INC, 2019). An MRI provides detailed images of the breast and is needed to assess the extent or spread of the cancer. Lab tests include hormone receptor and HER2/neu tests. When estrogen and progesterone are present on the cancerous cells, tumor growth accelerates (National Breast Cancer Foundation INC, 2019).