Breast Cancer


Breast cancer is the most commonly diagnosed cancer, besides skin cancer, found in women in the United States. Treatment advances are leading to more women with breast cancer living longer overall and without disease progression. The following information includes a brief description of how breast cancer develops and is classified, as well as an overview of the disease from diagnosis to follow-up care.

Development, diagnosis and classification

As with most cancers, breast cancer starts from one or several genetically abnormal cells, which divide and multiply to become a mass of abnormal cells (tumor). Most breast cancers begin in the milk ducts.

Noninvasive breast cancers include those that do not spread beyond the ducts. Those are called ductal carcinoma in situ (DCIS). Breast cancers that remain confined to the lobules (milk-secreting glands) are known as lobular carcinoma in situ (LCIS). While not life-threatening, both increase the risk of later developing an invasive breast cancer. Most breast cancers are invasive and spread beyond the tissue where they arise. Invasive ductal cancers are by far the most common, but several other subtypes exist (see Table 1).

Figure 1. Anatomy of the breast

While screening tests such as mammograms, ultrasound and magnetic resonance imaging (MRI) are commonly used to detect breast changes, a biopsy is the only way to know if cancer is present. For a biopsy, a sample of the suspicious area, called a biopsy specimen, is taken and tested in the lab by a pathologist. If your biopsy results indicate cancer, staging is the next step.

Breast cancer is categorized by stages, depending on whether tumor cells have broken off from the tumor and traveled through the lymphatic system to lymph nodes (tiny, bean-shaped organs that are part of the immune system), or through the bloodstream to other parts of the body. Learn more about staging here.

Table 1. Types of breast cancer

Type Prevalence Characteristics
Ductal carcinoma in situ (DCIS) 80% Remains confined to the milk ducts
Lobular carcinoma in situ (LCIS) 20% Remains confined to the lobules
Invasive (Infiltrating)
Ductal 80% Arises from the milk ducts and spreads beyond
Lobular 10% Arises from the lobules and spreads beyond
Medullary 3-5%* Soft, fleshy tumor, often associated with BRCA1 mutation
Mucinous (colloid) 2-3% Mucus is primary component of tumor, less likely to spread to lymph nodes
Papillary 1-2% Tumor has small, finger-like projections; usually occurs with DCIS
Tubular 1-2% Small tumor, less likely to spread beyond breast
Cribriform 5-6% Cancer cells invade connective tissue and cancer cells have “holes”
Inflammatory 1-5%* Redness and swelling of the breast, often without a distinct lump
Receptor subtypes
Hormone receptor (ER or PR) positive and HER2-negative 60-70% Tumor is positive for either ER or PR and negative for HER2
HER2-positive 15-20% HER2 is positive and includes any ER or PR status
Triple-negative 10-20% Tumor is negative for estrogen and progesterone receptors and does not overexpress HER2

*Prevalence among all breast cancer cases

New ways of defining breast cancer

Breast cancer was once considered one general disease, but researchers have found that tumors vary in several important ways. As a result, more specific treatments are now available depending on a person’s specific tumor type. Tumors are still classified according to how they look under the microscope (known as the “histologic” type), but the identification of biomarkers and the development of technology for genetic profiling (studying several genes in a tumor simultaneously) have led to an additional classification of breast cancer based on molecular subtypes (See Tumor Markers). Based on this research, significant advancements continue to provide additional treatment options for the different types of breast cancer.

Top Ten Things You Should Know About Breast Cancer

  1. No two breast cancers are exactly alike.

    As a result, the “best” treatment plan for each woman differs. The personalized approach to breast cancer treatment involves making decisions on the basis of many factors, including the type of cancer, the stage of disease, the results of biomarker testing, the genetic make-up of the tumor and a woman’s individual preferences.

  2. Breast cancer can be treated in a variety of settings.

    Cancer treatment centers may be freestanding facilities or they may be affiliated with a community hospital or an academic teaching hospital. Some cancer centers have been recognized by the National Cancer Institute (NCI) for their scientific excellence and extensive cancer-related resources. These centers are described as “NCI-designated cancer centers.” Centers accredited by the National Accreditation Program for Breast Centers (NAPBC) also offer benefits for women with breast cancer. See list of centers.

  3. It is acceptable to seek a second opinion.

    Getting a second opinion from another pathologist with extensive expertise in examining breast cancers can be of benefit, especially if there was difficulty or controversy in interpreting the initial findings. Getting a second opinion about the recommended treatment plan can also be of benefit. Many health insurance policies will cover a second opinion if you or your doctor requests it. The delay of getting a second opinion usually does not affect the outcome of treatment, but be sure to ask your doctor about this.

  4. Clinical trials offer benefits to many women with breast cancer.

    People who have participated in a clinical trial have identified several advantages, including having access to the best available care, playing an active role in their own health care, and making a valuable contribution to cancer research. Some risks may also be involved. Talk to your doctor or another member of your treatment team to learn more about clinical trials for which you may be eligible. Learn more about clinical trials.

  5. A team of health care professionals will be involved in your care.

    Because most women with breast cancer receive more than one type of treatment, care is planned and given by a team of health care specialists rather than just one physician. The treatment team usually involves a breast surgeon or surgical oncologist, radiation oncologist, medical oncologist, breast radiologist, pathologist, and a breast reconstructive surgeon. Additional health care professionals, such as nurses, physician assistants, nutritionists, social workers and others may also collaborate to provide optimal care. See Multipidisciplinary Team for more information.

  6. You should be an active participant in decision-making.

    Learn as much as you can about your particular type of cancer so that you can be fully informed and prepared to participate in the decision-making about treatment. Your doctors will discuss options, and family and friends may offer advice. But the “right” treatment decision is the one that’s best for you, based on your own perceptions of quality of life. Consider asking each of the doctors on your team about the benefits and side effects of their portion of therapy. See Treatment Option Charts.

  7. Side effects of treatment can be alleviated.

    Treatments for breast cancer may cause side effects, but there are now many ways to manage them. Talk to your doctor about the potential side effects of the treatment or treatments you’ve chosen and ask if there are ways to prevent or reduce these side effects. Be sure to tell your doctor or other members of your treatment team about symptoms you have so they can be managed promptly.

  8. Help is available for financial and practical issues.

    A variety of resources are available to help with expenses related to prescriptions, travel and health care equipment. Advocacy groups and community-based organizations often offer help with child care, provide transportation and even supply wigs. Ask social workers in your cancer center for information on local resources and be sure to review our list of resources for financial assistance.

  9. Support groups offer comfort and strength.

    Support groups provide an opportunity to talk with people who are facing some of the same challenges or have undergone similar treatments. Sharing your experience with others and hearing about their experiences can help reduce feelings of isolation. Many support groups are available online if you’d rather interact with others that way. Be sure to review our list of support groups.

  10. You can take control.

    A diagnosis of breast cancer is overwhelming, and it is easy to feel as if your life is out of control. But you have the power to overcome the challenges of breast cancer. Don’t be afraid to tell your doctors about your treatment preferences. Take good care of yourself by getting proper nutrition, exercise and sleep. Do whatever it takes to help you heal and feel physically and emotionally healthy, whether it be meditation, yoga, relaxation techniques, spirituality or counseling. Spend time with family and friends and be specific about what you need — and don’t need — from them. Enjoy your favorite activities. Live every day to its fullest.




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