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What Is Breast Cancer?

Breast cancer occurs when cells in the breast tissue develop changes (mutations) in their DNA, causing the cells to grow out of control. These abnormal cells form a tumor that can destroy normal body tissues and structures.

Breast cancer usually develops in either the lobules or the ducts of the breast. Lobules are the glands that produce milk, and ducts are the pathways that carry the milk from the glands to the nipples. Breast cancer can also occur in the fatty tissue or the fibrous connective tissue of the breast.

Breast cancer is the most common cancer diagnosed in women in the United States. About one in eight women will develop breast cancer at some point in their life.

According to the American Cancer Society, more than 281,500 new cases of invasive breast cancer and nearly 49,300 new cases of ductal carcinoma are diagnosed in the U.S. each year, resulting in about 43,600 deaths. In Colorado, there are approximately 4,580 new cases of breast cancer each year.

Although breast cancer occurs primarily in women, men can also develop the disease.

Breast Cancer Prognosis and Survival Rates

Breast cancer is the second leading cause of cancer death in women (after lung cancer) in the U.S. However, the number of women who died of breast cancer decreased by 40% from 1989 to 2007. Experts believe this was largely due to increased breast cancer screening, as well as advances in the diagnosis and treatment of breast cancer.

Since 2007, the number of women under age 50 who have died of breast cancer has plateaued, but the number of women age 50 and older who have died of the disease has continued to decrease.

The prognosis for a patient with breast cancer depends on the type of cancer and the stage at which it is diagnosed. The earlier breast cancer is detected and treated, the better the prognosis.

The five-year survival rate for patients with localized breast cancer (where the cancer has not spread outside of the breast to any lymph nodes or other sites in the body) is 99%. The majority of cases (about 62%) are diagnosed at this stage, although younger women are less likely to be diagnosed at this stage than older women, likely because most breast cancer screening does not begin until age 40. The survival rate for node-positive breast cancer (where the cancer has spread outside the breast to nearby structures or lymph nodes) is 86%.

The survival rate drops as the cancer spreads beyond the immediate area of the breast. The five-year survival rate for patients with metastatic breast cancer, where the cancer has spread to distant parts of the body such as the lungs, liver, or bones, is 28%. This accounts for about 6% of all initial breast cancer diagnoses.

Why Come to CU Cancer Center for Breast Cancer

As the only National Cancer Institute Designated Comprehensive Cancer Center in the state of Colorado and one of only four in the Rocky Mountain region, the University of Colorado Cancer Center has doctors who provide state-of-the-art, multidisciplinary, patient-centered breast cancer care and researchers focused on diagnostic and treatment innovations.

The CU Cancer Center is home to the Diane O'Connor Thompson Breast Center on the Anschutz Medical Campus in Aurora, Colorado; the UCHealth Breast Center – Cherry Creek in Denver; the UCHealth Breast Center - Highlands Ranch Hospital in Highlands Ranch; and the UCHealth Lone Tree Breast Center These multidisciplinary clinics offer patients an “all in one” approach to clinical care, overseen by world-class medical oncologists, surgical oncologists, plastic and reconstructive surgeons, radiation oncologists, radiologists, genetic counselors, physical therapists, lymphedema therapists, breast imaging patient navigators, breast cancer nurse navigators, and others who collaborate on both primary treatment and aftercare.

Oncology Nurse Turned Cancer Survivor Is Dedicated to Improving the Quality of Care for Patients

There are numerous breast cancer clinical trials being conducted by CU Cancer Center members all the time. These trials offer patients additional treatment options investigating new treatments designed to improve patient outcomes.

The Women’s Cancer Developmental Therapeutics Program (WCDTP) at the CU Cancer Center seeks to increase the development of novel cancer therapies in ovarian cancer and other gynecologic cancers with the goal of decreasing cancer-related morbidity and mortality for patients. Additionally, the WCTD seeks to increase access to phase I and II clinical trials of novel cancer therapies for patients with gynecologic and breast cancers.

CU doctors are also experienced in treating a variety of benign (non-cancerous) breast conditions. Although benign breast conditions are not life-threatening, some are linked with a higher risk of developing breast cancer later in life. The CU breast cancer risk assessment and prevention program offers the tools and experience to determine patient risk.

Some non-cancerous breast conditions include breast pain, nipple discharge, fibrosis and simple cysts, ductal or lobular hyperplasia, atypical proliferative changes, adenosis, fibroadenomas, intraductal papillomas, granular cell tumors, fat necrosis, oil cysts, mastitis, and duct ectasia, phyllodes tumors, and high-risk proliferative lesions.

Our clinical partnership with UCHealth has produced survival rates higher than the state average for all stages of breast cancer.

Breast Cancer Graphic

Number of Patients Diagnosed – UCHealth 3,035 – State of Colorado 14,137
Number of Patients Surviving – UCHealth 2,631 – State of Colorado 12,031
*n<30, 5 Year Survival – (Date of diagnosis 1/1/2010–12/31/2014)

Types of Breast Cancer

Different types of breast cells can become cancerous, and the type of cell affected determines the type of breast cancer. Breast cancers are categorized by looking at the cells under a microscope. Doctors use this information to understand the expected growth pattern and speed, as well as which treatments may work best.

Most breast cancers are carcinomas: tumors that start in the epithelial cells that line organs and tissues throughout the body. When tumors form in the breast, they are usually a specific type of carcinoma called adenocarcinoma, which starts in the cells of the lobules (the milk-producing glands of the breast) or the milk ducts (the pathways that carry milk from the lobules to the nipples).

Breast cancers can also be categorized based on whether the tumor has spread or not. They are divided into two main categories: non-invasive (also called in situ) and invasive (also called infiltrating).

Common Non-Invasive Breast Cancers

Ductal carcinoma in situ (DCIS) tumors are confined to the milk ducts and have not invaded the surrounding breast tissue.

Lobular carcinoma in situ (LCIS) tumors grow in the lobules and have not invaded the surrounding breast tissue.

Common Invasive Breast Cancers

Invasive ductal carcinoma (IDC) is the most common type of breast cancer. These tumors have developed in the milk ducts and invaded nearby breast tissue.

Invasive lobular carcinoma (ILC) tumors have developed in the lobules and have invaded nearby breast tissue.

Once the tumor has spread outside the lobules or milk ducts, it can begin to spread to other nearby tissues, lymph nodes, and organs.

Rare Breast Cancers

Inflammatory breast cancer (IBC) is a rare and aggressive type of invasive breast cancer that accounts for only 1% to 5% of all breast cancer diagnoses. IBC causes cells to block the lymph channels and nodes near the breast, preventing them from draining properly. Instead of forming a tumor, IBC causes the breast to swell. The breast may appear red and feel warm, pitted and thick, like an orange peel. This type of breast cancer tends to grow and spread quickly.

Paget’s disease is a rare condition, accounting for only about 1% to 3% of breast cancer diagnoses. It begins in the ducts of the nipple and spreads to the skin and areola of the nipple. Although it is usually non-invasive, it can become invasive.

Phyllodes tumor is an extremely rare type of breast cancer that forms in the connective tissue (or stroma) of the breast. Although most phyllodes tumors are benign, some can become cancerous (or malignant).

Angiosarcoma is a rare type of tumor that grows in the blood vessels or lymph vessels of the breast and accounts for less than 1% of all breast cancer diagnoses.

Risk Factors for Breast Cancer

Breast cancer occurs when some breast cells begin to multiply rapidly, accumulating to form a lump or mass called a tumor. Researchers have identified several hormonal, lifestyle, and environmental factors that may increase a person’s risk of developing breast cancer. These are called risk factors. 

Gender: Women are 70 to 100 times more likely than men to develop breast cancer.

Age: The risk of breast cancer increases with age. Most invasive breast cancers are diagnosed in women over age 55.

Race and ethnicity: People with Ashkenazi or Eastern European Jewish ancestry may be more likely to get breast cancer. White women are more likely to develop breast cancer than Black women. However, among women younger than 45, the disease is more common in Black women than in white women. Black women are also more likely to die from the disease. Hispanic, Asian/Pacific Islander, and American Indian/Alaska Native women are the least likely to get breast cancer.

Height: Studies have found that taller women have a higher risk of breast cancer than shorter women. 

Dense breast tissue: Women with dense breast tissue (made up of more glandular and fibrous tissue and less fatty tissue) have a higher risk of breast cancer than women with average breast density.

Personal history of breast conditions: Patients who have been diagnosed with certain conditions such as atypical ductal hyperplasia, atypical lobular hyperplasia, lobular carcinoma in situ, and papillomatosis have an increased risk of breast cancer.

Personal history of breast cancer: Patients who have already had breast cancer in one breast have an increased risk of developing cancer in the other breast.

Family history and genetics: People with a mother, sister, or daughter who has been diagnosed with breast cancer have a higher risk of developing breast cancer. Those with a family history of ovarian cancer, metastatic prostate cancer, or pancreatic cancer may also have an increased risk of breast cancer.

Several inherited gene mutations can increase the risk of breast cancer, particularly the tumor suppressor gene mutations BRCA1, BRCA2, and PALB2. Other gene mutations or hereditary conditions that may increase a person’s risk of breast cancer include Lynch syndrome, Cowden syndrome, Li-Fraumeni syndrome, Peutz-Jeghers syndrome, Bannayan-Riley-Ruvalcaba syndrome, ataxia telangiectasia, hereditary diffuse gastric cancer, and the CHEK2 gene.

Radiation exposure: People who received radiation treatments to the chest as a child or young adult have an increased risk of breast cancer.

Weight: People who are overweight or obese have an increased risk of breast cancer.

Early menstruation: Women who started menstruating before age 12 have a higher risk of breast cancer.

Late menopause: Women who begin menopause after age 55 are more likely to develop breast cancer.

Having a first child at an older age: Women who give birth to their first child after age 35 may have a greater risk of breast cancer.

Having never been pregnant: Women who have never been pregnant have a higher risk of developing breast cancer than do women who have had one or more pregnancies.

Not breastfeeding: Research suggest that breastfeeding may slightly lower breast cancer risk, especially when it is continued for a year or more.

Postmenopausal hormone therapy: Women who take hormone therapy medications to treat the symptoms of menopause have a higher risk of breast cancer.

Hormonal birth control: Some studies suggest that the use of oral contraceptives and other hormonal birth control methods such as the Depo-Provera shot and hormone-releasing IUDs, implants, patches, and rings may slightly increase the risk of breast cancer.

Alcohol consumption: Drinking alcohol increases the risk of breast cancer.

Breast implants: Although breast implants have not been linked to an increased risk of the most common types of breast cancer, recipients may be more like to develop a rare type of non-Hodgkin lymphoma called breast implant-associated anaplastic large cell lymphoma, which can form in scar tissue around the implant.

Exposure to diethylstilbestrol (DES): From the 1940s to the early 1970s, some pregnant women were given an estrogen-like drug called DES that was thought to lower their chances of miscarriage. Women who took DES and women whose mothers took DES have a slightly higher risk of developing breast cancer.  

Preventing Breast Cancer

In addition to avoiding the risk factors above (when possible) and maintaining a healthy lifestyle through diet and exercise, some women with a heightened risk of breast cancer may explore preventive measures such as:

Genetic counseling and testing: Women with a family history of breast cancer may benefit from genetic counseling. A genetic counselor will review the patient’s family history to see how likely it is that they have a family cancer syndrome such as Hereditary Breast and Ovarian Cancer (HBOC) syndrome, which is linked to mutations in the BRCA1 and BRCA2 genes. If so, they may recommend blood panel tests to look for these and other gene mutations that can increase a person’s risk for breast cancer. These findings can help guide further preventive measures and screenings.

Preventive medications: Some hormone-blocking drugs can help prevent breast cancer. This approach is called chemoprevention or endocrine prevention. These drugs include medicines like tamoxifen and raloxifene that block the action of estrogen in breast tissue or aromatase inhibitors that block overall estrogen production.

Preventive surgery: Women with a very high risk of breast cancer, such as those with a BRCA gene mutation, may choose to have their breasts surgically removed as a preventive measure. This is called a prophylactic mastectomy and reduces the risk of developing breast cancer by 90% to 95%. Prophylactic mastectomies can be performed with immediate breast reconstruction with the breast surgeon working with the plastic surgeon. When possible, nipple-sparing mastectomies are offered to enhance the long-term cosmetic outcomes of the procedure. Preventive mastectomies eliminate the need to have screening mammograms and MRIs. However, since there is a small amount of remaining breast tissue, high-risk women are taught how to monitor the skin for any changes.

Women with a high risk of breast and ovarian cancer may also consider the preventive removal of the ovaries and fallopian tubes, since the ovaries are the body’s main source of estrogen. This is called a prophylactic salpingo-oophorectomy and reduces the risk of both breast cancer and ovarian cancer. Some women choose to initially remove only the fallopian tubes (salpingectomy) and retain the ovaries in order to preserve fertility. Salpingectomy may reduce the risk of ovarian cancer. Once childbearing is complete (or if a woman is unable to or chooses not to have children), the ovaries can be removed. Preventive removal of the ovaries is not recommended prior to age 35 or before a woman has completed her childbearing. Timing of preventive surgery is a personal decision.

Scarlet Doyle's Breast Cancer Journey

Latest in Breast Cancer from the CU Cancer Center

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Information reviewed by Jennifer Diamond, MD, in April 2022.