Cells in the body normally divide (reproduce) only when new cells are needed. Sometimes, cells in a part of the body grow and divide out of control, which creates a mass of tissue called a tumor. If the cells that are growing out of control are more normal cells, the tumor is called benign (not cancerous). If, however, the cells that are growing out of control are abnormal, don't function like the body's normal cells, and begin to invade other tissue, the tumor is called malignant (cancerous).
Cancers are typically named after the part of the body from which they originate. Breast cancer originates in the breast tissue. Like other cancers, breast cancer can invade and grow into the tissue surrounding the breast. It can also travel to other parts of the body and form new tumors, a process called metastasis.
What Causes Breast Cancer?
We do not know what causes breast cancer, although we do know that certain risk factors may put you at higher risk of developing it. A person's age, genetic factors, personal health history, and diet all contribute to breast cancer risk.
Who Gets Breast Cancer?
Breast cancer ranks second as a cause of cancer death in women (after lung cancer). Today, about 1 in 8 women (12%) will develop breast cancer in her lifetime. The American Cancer Society estimated that in 2017, about 252,710 women will be diagnosed with invasive breast cancer and about 40,610 will die from the disease.
Only 5% to 10% of breast cancers occur in women with a clearly defined genetic predisposition for the disease. The majority of breast cancer cases are "sporadic," meaning there is no direct family history of the disease. The risk for developing breast cancer increases as a woman ages.
What Are the Symptoms of Breast Cancer?
The symptoms of breast cancer include:
- Lump or thickening in or near the breast or in the underarm that persists through the menstrual cycle.
- A mass or lump, which may feel as small as a pea.
- A change in the size, shape, or contour of the breast.
- A blood-stained or clear fluid discharge from the nipple.
- A change in the feel or appearance of the skin on the breast or nipple (dimpled, puckered, scaly, or inflamed).
- Redness of the skin on the breast or nipple.
- A change in shape or position of the nipple
- An area that is distinctly different from any other area on either breast.
- A marble-like hardened area under the skin.
What Are the Types of Breast Cancer?
The most common types of breast cancer are:
- Invasive (or infiltrating) ductal carcinoma. This cancer starts in the milk ducts of the breast. Then it breaks through the wall of the duct and invades the fatty tissue of the breast. This is the most common form of breast cancer, accounting for 80% of invasive cases.
- Ductal carcinoma in situ (DCIS) is ductal carcinoma in its earliest stage (stage 0). "In situ" refers to the fact that the cancer hasn't spread beyond its point of origin. In this case, the disease is confined to the milk ducts and has not invaded nearby breast tissue. If untreated, ductal carcinoma in situ may become invasive cancer. It is often curable.
- Infiltrating (invasive) lobular carcinoma. This cancer begins in the lobules of the breast where breast milk is produced, but has spread to surrounding tissues or other parts of the body. It accounts for about 10% of invasive breast cancers.
- Lobular carcinoma in situ (LCIS) is cancer that is only in the lobules of the breast. It isn't a true cancer, but serves as a marker for the increased risk of developing breast cancer later. Thus, it is important for women with lobular carcinoma in situ to have regular clinical breast exams and mammograms.
In addition, there are several other less common types of breast cancer.
What Are the Stages of Breast Cancer?
- Early stage or stage 0 breast cancer is when the disease is localized to the breast with no evidence of spread to the lymph nodes (carcinoma in situ).
- Stage I breast cancer: The cancer is 2 centimeters or less in size and it hasn't spread anywhere.
- Stage IIA breast cancer is a tumor smaller than 2 centimeters across with lymph node involvement or a tumor that is larger than 2 but less than 5 centimeters across without underarm lymph node involvement.
- Stage IIB is a tumor that is greater than 5 centimeters across without underarm lymph nodes testing positive for cancer or a tumor that is larger than 2 but less than 5 centimeters across with lymph node involvement.
- Stage IIIA breast cancer is also called locally advanced breast cancer. The tumor is larger than 5 centimeters and has spread to the lymph nodes under the arm or near the breastbone, or a tumor that is any size with cancerous lymph nodes that adhere to one another or surrounding tissue.
- Stage IIIB breast cancer is a tumor of any size that has spread to the skin or chest wall.
- Stage IIIC breast cancer is a tumor of any size that has spread more extensively and involves more lymph node invasion.
- Stage IV breast cancer is defined as a tumor, regardless of size, that has spread to places far away from the breast, such as bones, lungs, liver, brain, or distant lymph nodes.
How Is Breast Cancer Diagnosed?
During your regular physical exam, your doctor will take a careful personal and family history and perform a breast exam and possibly order a mammogram or an ultrasound of the breasts. In certain women who are at increased risk for breast cancer, an MRI may be ordered.
Based on the results of these tests, your doctor may or may not request a biopsy to get a sample of the breast mass cells or tissue.
After the sample is removed, it is sent to a lab for testing. A pathologist -- a doctor who specializes in diagnosing abnormal tissue changes -- views the sample under a microscope and looks for abnormal cell shapes or growth patterns. When cancer is present, the pathologist can tell what kind of cancer it is (ductal or lobular carcinoma) and whether it has spread beyond the ducts or lobules (invasive).
Lab tests such as hormone receptor tests (estrogen and progesterone) can show whether these hormones help the cancer to grow. If the test results show that these hormones help the cancer grow (a positive test), the cancer is likely to respond to hormonal treatment. This therapy deprives the cancer of the estrogen hormone.
Breast cancer diagnosis and treatment are best accomplished by a team of experts working together with the patient. Each patient needs to evaluate the advantages and limitations of each type of treatment, and work with her team of doctors to develop the best approach.
How Is Breast Cancer Treated?
If the tests find breast cancer, you and your doctor will develop a treatment plan to eradicate the breast cancer, to reduce the chance of cancer returning in the breast, as well as to reduce the chance of the cancer traveling to a location outside of the breast. Treatment generally follows within a few weeks after the diagnosis.
The type of treatment recommended will depend on the size and location of the tumor in the breast, the results of lab tests done on the cancer cells, and the stage or extent of the disease. Your doctor usually considers your age and general health as well as your feelings about the treatment options.
Breast cancer treatments are local or systemic.
- Local treatments are used to remove, destroy, or control the cancer cells in a specific area, such as the breast. Surgery and radiation treatment are local treatments.
- Systemic treatments are used to destroy or control cancer cells all over the body. Chemotherapy; hormone therapy such as tamoxifen (Nolvadex, Tamoxen, Soltamox); aromatase inhibitors such as anastrozole (Arimidex), exemestane (Aromasin), and letrozole (Femara); and biologic drugs such as lapatinib (Tykerb), palbociclib (Ibrance), pertuzumab (Perjeta), trastuzumab (Herceptin), and trastuzumab emtansine (Kadcyla), are systemic treatments. A patient may have just one form of treatment or a combination, depending on her needs.
- Ribociclib (Kisquali) is used in combination with an aromatase inhibitor as initial hormone therapy in women who have gone through menopause who have hormone receptor positive, HER2-negative advanced breast cancer.
What Happens After Treatment?
Following local breast cancer treatment, your doctors will determine the likelihood that the cancer will recur outside the breast. This team usually includes a medical oncologist, a specialist trained in using medicines to treat breast cancer. The medical oncologist, who works with the surgeon, may advise the use of hormone therapy or possibly chemotherapy. These treatments are used in addition to, but not in place of, local breast cancer treatment with surgery and/or radiation therapy.
How Can I Protect Myself From Breast Cancer?
Follow these three steps for early breast cancer detection:
- Annual screening mammography between the ages of 40 to 50. The American Cancer Society recommends mammograms start at age 45. Breast cancer experts don't agree when women need to begin getting mammograms. Ask your doctor.
- Women in high-risk categories should have screening mammograms every year and typically start at an earlier age. MRI or ultrasound screening can also be given in addition to mammograms. Discuss the best approach with your doctor.
- Have your breasts examined by a health care provider at least once every three years after age 20, and every year after age 40. Clinical breast exams can complement mammograms.