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Medically reviewed by Dr.C.H. Weaver M.D. 5/2022

Breast cancer is a common cancer, with more than 232,000 individuals diagnosed in the United States each year.1 The disease occurs most frequently in women, but can also occur in men.

The normal breast has 6 to 9 overlapping sections called lobes and within each lobe are several smaller lobules that contain the cells that produce milk. The lobes and lobules are linked by thin tubes called ducts, which lead to the nipple in the center of the breast. The spaces around the lobules and ducts are filled with fat. Lymph vessels carry colorless fluid called lymph, which contains important immune cells. The lymph vessels lead to small bean-shaped structures called lymph nodes. Clusters of lymph nodes are found in the axilla (under the arm), above the collarbone, and in the chest.

A breast cancer begins when healthy cells in the breast change and grow out of control. Most breast cancers start in the ducts or lobes and are called ductal carcinoma or lobular carcinoma. Although breast cancer most commonly spreads to nearby lymph nodes, it can also spread further through the body to areas such as the bones, lungs, liver, and brain. When breast cancer spreads to other parts of the body or when breast cancer cells move to other parts of the body through the blood vessels and/or lymph vessels. This is called metastasis.

As a result of advocacy and advances in scientific knowledge our understanding of breast cancer continues to evolve. In recent years we have witnessed a steady improvement in the early detection of breast cancer, the prevention of breast cancer in high-risk individuals through genetic testing, and improved outcomes of individuals with both early and advanced stage disease. There is indeed much to be optimistic about.1,2

Symptoms & Signs of Breast Cancer

The suspicion of breast cancer often first arises when a lump is detected in the breast during breast examination or a suspicious area is identified during screening mammography. In order to diagnose the cause of the suspicious area or lump in the breast, a physician will perform a biopsy. Other signs and symptoms of breast cancer include:

  • Skin Changes with the Breast- skin can feel itchy develop redness in color. With inflammatory breast cancer, swelling and a dimpled look to the skin may occur.
  • Swelling- may occur as the cancer grows.
  • Nipple Discharge- Any type of fluid that comes from the nipple; yellow, the color of blood.
  • Pain- in the breast can be a warning.

What Causes Breast Cancer?

There are many types of breast tumors. Some breast tumors are benign (not cancerous). Benign breast tumors such as fibroadenomas or papillomas do not spread outside of the breast and are not life threatening. Other breast tumors are malignant (cancerous). The most common type of breast cancer is called ductal carcinoma and begins in the lining of the ducts. Another type of cancer is called lobular carcinoma, which arises in the lobules.

Breast cancer can be invasive or noninvasive. Invasive breast cancer is cancer that spreads into surrounding tissues. Noninvasive breast cancer does not go beyond the milk ducts or lobules in the breast.

  • Ductal carcinoma. Starts in the cells lining the milk ducts and make up the majority of breast cancers. Ductal carcinoma in situ (DCIS). This is cancer that is located only in the duct. Invasive or infiltrating ductal carcinoma. This is cancer that has spread outside of the duct.
  • Lobular carcinoma. Starts in the lobules. Lobular carcinoma in situ (LCIS). LCIS is located only in the lobules. LCIS is not considered cancer.
  • Inflammatory breast cancer is a faster growing more aggressive cancer accounting for ~ 5% of all breast cancers.

Less common types of breast cancer include:

  • Medullary
  • Mucinous
  • Tubular
  • Metaplastic
  • Papillary breast cancer

Genetics is extremely important; women with a family history of breast cancer in a first degree relative (mother, sister, or daughter) have an increased risk of breast cancer and often have inherited genes that increase their risk of developing breast cancer.1,2

Risk Factors for Developing Breast Cancer

  • Older age
  • A personal history of breast cancer or benign (non-cancer) breast disease
  • Family history of breast cancer
  • Genetic risk: BRCA1 and BRCA2 genes
  • Dense breasts31,32
  • Exposure of breast tissue to estrogen made in the body
  • Taking hormone therapy for symptoms of menopause
  • Prior radiation therapy to the breast or chest
  • Obesity
  • Drinking alcohol

Diagnosis & Tests for Breast Cancer

If a suspicious or a precancerous lesion is found in the breast, a biopsy and additional tests will be recommended to determine whether invasive cancer exists.

A biopsy can be performed on an outpatient basis. During a biopsy, a physician removes cells for examination in the laboratory to determine whether cancer is present. If the biopsy indicates that cancer is present, additional surgery may be performed after a course of treatment is selected.

When cancer is identified in the biopsy specimen, several other tests should also be performed on the specimen in order to further classify the cancer and determine the optimal treatment strategy. Based on the stage of the cancer and the results of these tests, treatment of breast cancer is personalized for each individual. Precision treatment may involve surgery, radiation therapy, systemic treatment with precision cancer medicines or chemotherapy, and/or hormonal therapy.

Diagnostic Tests that are used to Find Breast Cancer

  • Mammogram: An x-ray is taken when the breast is pressed between two plates.
  • Ultrasound: A procedure in which high-energy sound waves (ultrasound) are bounced off internal tissues or organs and make echoes. The echoes form a picture of body tissues called a sonogram.
  • Magnetic Resonance Imaging (MRI) A procedure that uses a magnet and radio waves to take a very detailed picture of both breasts. There are four types of biopsy used to check for breast cancer:

Types of Biopsies Used to Evaluate Breast Cancer

  • Excisional biopsy removes an entire lump of breast tissue.
  • Incisional biopsy removes part of a lump or a sample of breast tissue.
  • Core biopsy removes tissue using a wide needle.
  • Fine Needle Aspiration (FNA) biopsy removes tissue or fluid, using a thin needle.

Initial Staging of Breast Cancer

Stage is a measure of the extent of spread of the cancer. The first step in staging is to evaluate the cancer for “local” spread by assessing for the presence or absence of local axillary (under the arm) lymph node metastases adjacent to the breast. This may be assessed through either sentinel lymph node biopsy or axillary lymph node dissection.

Axillary lymph node dissection involves the removal of many axillary lymph nodes; the procedure can be associated with chronic side effects such as pain, limited shoulder motion, numbness, and swelling.

Sentinel lymph node biopsy involves the removal of only a small number of nodes, or even a single node. If the sentinel lymph nodes are negative (show no evidence of cancer), then no further lymph node surgery is required. Sentinel lymph node biopsy is becoming more widely adopted in the clinical setting for determining whether cancer has spread to the lymph nodes in women with localized breast cancer.

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Precision Medicine & Personalized Breast Cancer Care

The purpose of precision cancer medicine is to define the genomic alterations in the cancers DNA that are driving that specific cancer. Breast cancer used to be diagnosed solely by a visual microscopic examination of tumor tissue and patients received the same chemotherapy. Precision cancer medicine utilizes molecular diagnostic & genomic testing, including DNA sequencing, to identify cancer-driving abnormalities in a cancer’s genome. Once a genetic abnormality is identified, a specific targeted therapy can be designed to attack a specific mutation or other cancer-related change in the DNA programming of the cancer cells. Precision cancer medicine uses targeted drugs and immunotherapies engineered to directly attack the cancer cells with specific abnormalities, leaving normal cells largely unharmed. Precision medicines are being developed for the treatment of breast cancer and patients should ask their doctor about whether testing is appropriate.

HER2 status: Twenty to thirty percent of breast cancers over express (make too much of) a protein known as HER2. Over expression of this protein leads to increased growth of cancer cells. Fortunately, the development of treatments that specifically target HER2-positive cells has improved outcomes among women with HER2-positive breast cancer. For this reason, HER2 status should be accurately measured on all breast cancers.1

Hormone receptor status: Some breast cancer cells express an abundance of receptors for the female hormones estrogen and/or progesterone. These cancers– called hormone receptor-positive –are typically associated with a better prognosis and are treated differently from breast cancers that are hormone receptor-negative. Patients with hormone receptor-positive breast cancer often receive treatment with hormonal therapy, such as tamoxifen or an aromatase inhibitor.

Multigene Tests to Predict Recurrence: Among women with early-stage breast cancer, the expression, or activity, of certain genes has been linked with the likelihood of cancer recurrence.

  • Oncotype DX is a genomic test that predicts risk of recurrence among selected women with early-stage breast cancer, including women with ductal carcinoma in situ (DCIS).23
  • Mammaprint helps predict if early stage node negative breast cancer will spread to other parts of the body. If the risk that the cancer will spread is high, chemotherapy may be given to lower the risk.24

Use of these tests may help guide decisions about whether about additional treatment with chemotherapy or radiation therapy is necessary after surgery.

Triple Negative Breast Cancer: Approximately 12% of breast cancers are triple-negative breast cancers, meaning that they are estrogen-receptor negative (ER-), progesterone-receptor negative (PR-), and human epidermal growth factor receptor 2-negative (HER2-). This means that TNBC is not stimulated to grow from exposure to the female hormones estrogen or progesterone, nor through an overactive HER2 pathway.

Additional tests are necessary to determine if the cancer has spread beyond the breast to other parts of the body.

  • Chest x-ray: is a picture of the bones inside the chest. An x-ray is a type of energy beam that can go through the body and onto film, making a picture of areas inside the body.
  • Computed Tomography (CT) Scan: A CT scan is a technique for imaging body tissues and organs, during which X-ray transmissions are converted to detailed images, using a computer to synthesize X-ray data. A CT scan is conducted with a large machine positioned outside the body that can rotate to capture detailed images of the organs and tissues inside the body.
  • Magnetic Resonance Imaging (MRI): MRI uses a magnetic field rather than X-rays, and can often distinguish more accurately between healthy and diseased tissue than a CT. An MRI gives a better picture of cancer located near bone than does CT, does not use radiation, and provides pictures from various angles that enable doctors to construct a three-dimensional image of the cancer.
  • Positron emission tomography (PET): Positron emission tomography scanning is an advanced technique for imaging body tissues and organs. One characteristic of living tissue is the metabolism of sugar. Prior to a PET scan, a substance containing a type of sugar attached to a radioactive isotope (a molecule that emits radiation) is injected into the patient’s vein. The cancer cells “take up” the sugar and attached isotope, which emits positively charged, low energy radiation (positrons) that create the production of gamma rays that can be detected by the PET machine to produce a picture. If no gamma rays are detected in the scanned area, it is unlikely that the mass in question contains living cancer cells.
  • Bone Scan: A test to check if there are cancer cells, in the bone. A very small amount of radioactive material is injected into a vein and travels through the bloodstream. The radioactive material collects in the bones and is detected by a scanner.

Stages of Breast Cancer

Carcinoma In Situ: Approximately 15-20% of breast cancers are very early in their development. These are sometimes referred to as carcinoma in situ and consist of two types: ductal carcinoma in situ (DCIS), which originates in the ducts and lobular carcinoma in situ (LCIS), which originates in the lobules. DCIS is the precursor to invasive cancer and LCIS is a risk factor for developing cancer.

Stage I: Cancer is confined to a single site in the breast, is less than 2 centimeters (3/4 inch) in size and has not spread outside the breast.

Stage IIA: Cancer has spread to involve underarm lymph nodes and is less than 2 centimeters (3/4 inch) in size or the primary cancer itself is 2-5 centimeters (3/4-2 inches) and has not spread to the lymph nodes

Stage IIB: Cancer has spread to involve underarm lymph nodes and/or the primary cancer is greater than 5 centimeters (2 inches) in size and does not involve any lymph nodes.

Stage IIIA: Cancer is smaller than 5 centimeters (2 inches) and has spread to the lymph nodes under the arm or the lymph nodes are attached to each other or to other structures or the primary cancer is larger than 5 centimeters (2 inches) and has spread to the lymph nodes under the arm.

Stage IIIB: Cancer directly involves the chest wall or has spread to internal lymph nodes on the same side of the chest.

Inflammatory: Inflammatory breast cancer is a special class of breast cancer that is rare. The breast looks as if it is inflamed because of its red appearance and warmth. The skin may show signs of ridges and wheals or it may have a pitted appearance. Inflammatory breast cancer tends to spread quickly.

Stage IV - Metastatic Breast Cancer has spread to distant locations in the body, which may include the liver, lungs, bones or other sites.

Local Recurrence of Breast Cancer the breast cancer has progressed or returned (recurred/relapsed) in the breast or chest wall following initial treatment.


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