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Breast cancer is the second most common cancer in women in the United States behind skin cancer. Overall, the average risk of a woman developing breast cancer sometime in her life is about one in eight. It mainly occurs in middle-aged and older women, with 62 being the median age at the time of diagnosis.
What is breast cancer?
Breast cancer is the uncontrolled growth of abnormal cells in one of several areas of the breast, including the ducts that carry milk to the nipple, lobules (glands that produce milk), and nonglandular tissue. Sometimes breast cancer stays in the tissue in which it began. But it can move into nearby tissue and lymph nodes.
Signs of breast cancer include:
- a lump or thickening in the breast or skin under the arm
- a clear or bloody discharge from the nipple
- crusting or scaling of the nipple
- an inverted nipple
- redness or swelling of the breast
- dimpling on the breast skin resembling the texture of an orange’s skin
- subtle changes in the position of the breast, such as one being higher than the other
- a sore or ulcer on the breast that does not heal
How is breast cancer diagnosed?
Diagnosis of breast cancer begins with a doctor’s exam to look for any signs and symptoms of breast cancer. Should your doctor discover a lump, or a mammogram detect an area of abnormal breast tissue, your doctor will recommend additional tests like an ultrasound or magnetic resonance imaging (MRI).
Ultrasound can confirm whether the lump is a solid tumor or a fluid-filled, noncancerous cyst. It can also be used to assess any abnormal areas found on a mammogram.
Although it is not routinely performed, MRI is used to assess abnormalities on a mammogram, get a more accurate estimate of a cancer's size, and check for other cancers.
If the lump is solid, your doctor probably will recommend a breast biopsy. During a biopsy, a small amount of breast tissue is removed and analyzed in a laboratory.
A breast biopsy can be done in different ways. These include:
- fine-needle aspiration, which uses a thin needle to withdraw tissue from the tumor
- large core needle biopsy, which allows larger pieces of tissue to be removed
- stereotactic needle biopsy, a type of large core needle biopsy, uses special imaging equipment to pinpoint the tissue to be removed
- surgical biopsy, which involves removing all or part of the breast lump
The type of biopsy your doctor chooses will depend on the location of the lump, its size, and other factors.
A specialist called a pathologist will examine the tissue under a microscope to determine whether the tissue contains cancer cells. If it does, the pathologist can determine the type of breast cancer.
What are breast cancer risk factors?
Age and genetics are the leading risk factors for breast cancer. More than three out of four breast cancer cases occur in women over age 50. Those with a family history of the disease (mother, sister, grandmother) are also at high risk, as are women with dense breasts. Another genetic risk factor is a mutation of the BRCA1 or BRCA2 gene.
Race also plays a role. Black women have a higher risk of developing breast cancer before age 40 than white women and are more likely to die than any other race or ethnic group.
Other risk factors for breast cancer include the following:
- being of Ashkenazi Jewish descent
- being a current smoker or having smoked for 10 or more years
- having previously had breast cancer or a benign breast condition
- having had radiation to the chest or breast between the ages of 10 and 30
- increased exposure to the female hormone estrogen. For instance, having a first menstrual period before age 13, entering menopause after age 51, or using estrogen replacement therapy for more than five years
- never having been pregnant or having a first pregnancy after age 30
- being overweight, especially after menopause
- drinking alcohol (cancer risk doubles with three or more drinks per day)
- having a sedentary lifestyle with little regular exercise
- having undergone a prior breast biopsy
Having several risk factors doesn't mean a woman will inevitably develop breast cancer. Likewise, having fewer risk factors doesn't offer 100% protection against it.
Although there are no guarantees, women can take steps to help prevent breast cancer. For example:
- Maintain a healthy weight.
- Exercise regularly.
- Limit the use of alcohol. (Experts recommend no more than one drink per day for women and two drinks per day for men.)
- Have regular mammograms. Experts differ on whether women at average risk for breast cancer should begin screening at age 45 or 50. They also disagree on the ideal frequency of mammography, either yearly or once every two years. Talk with your doctor about what is best for you.
Are there different types of breast cancer?
Noninvasive (in situ) breast cancers are those that haven't spread into the surrounding tissue. They include:
Ductal carcinoma in situ (DCIS). This occurs when cancer cells fill the ducts but haven't spread through the walls into fatty tissue. Nearly all women diagnosed at this early stage can be cured. Without treatment, about 20% of DCIS cases will lead to invasive breast cancer within 10 years.
Lobular carcinoma in situ (LCIS). A lesser threat than DCIS, LCIS develops in the breast's milk-producing lobules and can increase a woman's risk of developing cancer in other areas of the breasts.
Breast cancer is considered invasive when the cancer cells have penetrated the lining of the ducts or lobules (glands that make milk). This means the cancer cells can be found in the surrounding tissues, such as fatty and connective tissues or the skin.
These are the primary forms of invasive breast cancer:
Invasive ductal carcinoma. This type of breast cancer, which accounts for three-quarters of cases, develops in the milk ducts. Cancer breaks through the duct wall and invades the breast's fatty tissue. It then spreads (metastasizes) to other body parts through the bloodstream or lymphatic system.
Invasive lobular carcinoma. This type accounts for about 15% of cases. It originates in the breast's milk-producing lobules and can spread to the breast's fatty tissue and other areas of the body.
Paget's disease. This rare form of breast cancer begins in the milk ducts of the nipple and can spread to the dark circle around the nipple. Women with Paget's disease usually have a history of nipple crusting, scaling, itching, or inflammation.
Inflammatory carcinoma. Another rare breast cancer, this form can seem like an infection because there is usually no lump or tumor. The skin is red, warm, and looks pitted like an orange peel. Because it spreads quickly, inflammatory carcinoma is the most aggressive and difficult to treat of all breast cancers.
Triple negative breast cancer: This type accounts for about 10% to 15% of all breast cancers. It refers to cancer cells not being fueled by estrogen and progesterone hormones or the protein HER2. The cancer is more common in women younger than age 40, Black women, or those who have a BRCA1 gene mutation.
What are the stages of breast cancer?
Once breast cancer is diagnosed, doctors designate its stage, which describes the cancer’s size and how far it’s spread. This helps determine the best treatment strategy.
Doctors stage the cancer using the TNM scale, which stands for Tumor, (lymph) Nodes, and Metastasis. T refers to the tumor’s size, N indicates whether the cancer has moved to lymph nodes, and M specifies whether it has spread to other areas of the body.
Other information may be collected to help determine the cancer’s stage; for instance, whether the cancer has estrogen or progesterone hormone receptors or produces too much HER2, a protein that helps breast cancer cells grow.
There are five breast cancer stages: zero through four. The higher the number, the more advanced the cancer. There are often several subcategories within each stage.
Stage 0. Also known as in situ, this indicates that cancer has not spread to nearby tissue.
Stage 1. Cancer has spread to surrounding breast tissue but is contained in a small area. It is also known as localized.
Stage 2. The cancer is in a limited breast region but has grown larger, and some lymph nodes are involved.
Stage 3. The cancer has spread more into the breast and possibly to the skin. The tumor is larger than in earlier stages, and more lymph nodes are affected.
Stage 4. The most advanced stage indicates that cancer has spread to nearby lymph nodes and other areas, such as the lungs, liver, brain, or bones.
What are the treatment options for breast cancer?
Early diagnosis significantly improves the outlook for breast cancer. If the tumor is small and confined to the breast, more than 90% of women survive five years or longer. However, if the disease spreads throughout the body before diagnosis, that rate drops to less than 20%. Cancer in one breast puts women at a higher than average risk of developing cancer in the other breast.
Treatment usually begins with a decision about the type of surgery. Factors taken into consideration when considering surgery include: the type of breast cancer; the characteristics of the original biopsy material; and patient preferences.
The surgery options include a mastectomy (removal of the affected breast, usually with some of the lymph nodes located in the armpit) or lumpectomy (removal of the tumor and a small amount of surrounding tissue).
After surgery, your doctor may recommend radiation therapy, chemotherapy, hormone therapy, targeted therapy, or a combination. Additional therapies decrease the risk of cancer returning or spreading. Here is a look at each one.
Radiation therapy. Radiation therapy usually is recommended after a lumpectomy to destroy remaining cancer cells and help prevent cancer from returning. Without radiation therapy, the odds of cancer returning increase by about 25%.
Chemotherapy. The need for chemotherapy depends on how much the cancer has spread and the tumor's molecular characteristics. In some cases, chemotherapy is recommended before surgery to shrink a large tumor so it can be removed more easily. Chemotherapy is usually necessary if the cancer does return.
Hormone therapy. Hormone therapy usually is recommended if the cancer is estrogen-receptor positive. One drug often used in these cases is tamoxifen. It blocks estrogen from attaching to receptors on breast cancer cells, preventing the hormone from delivering signals to the cells to grow and multiply. This may reduce the chances that cancer will return by up to 30%. Aromatase inhibitors are another common form of hormone therapy and are often used in postmenopausal women. These drugs decrease the amount of estrogen in the body by blocking estrogen production in all other tissues except the ovaries.
Targeted therapy. Drugs that target specific genetic changes to attack cancer cells are called targeted therapies. Your doctor can choose drugs most likely to attack your cancer based on your genetic markers.
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