Breast Cancer Facts

What is Breast Cancer?

Breast cancer is a disease in which breast tissue cells start growing abnormally and uncontrollably. It is the second most frequently diagnosed cancer among women in the United States, after skin cancer. This condition may also affect men, although it's rare.

There are different types of breast cancer. The most common is ductal carcinoma, which begins in the breast ducts – tubes that carry breast milk to the nipple. Less common breast cancer types include: lobular carcinoma, which starts in the tissues that make breast milk; and inflammatory breast cancer, which can cause swelling and inflammation of the breast.

Types of Breast Cancer

There are several kinds of breast cancer. The most common types are ductal carcinoma and lobular carcinoma. Breast cancers are usually described as “invasive” or “in situ.” Invasive – or infiltrating – cancers have spread into the surrounding breast tissue. In situ breast cancers are still in the location where they formed.

  • Ductal carcinoma is the most frequently diagnosed form of breast cancer, accounting for about one in five new cases. Ductal carcinoma starts when tumors form in the cells of the ducts that carry milk to the nipples. In situ ductal carcinoma has a very high chance of successful treatment if detected early, through a combination of observation, medication and surgery.
A cancerous tumor within the breast tissue.
  • Lobular carcinoma begins in the lobes or lobules of the breast. Each breast has 15 to 20 lobes. Each lobe includes smaller sections called lobules, where breast milk is produced. Lobular carcinoma is more often found in both breasts than other types of breast cancer. When found in situ, it rarely becomes invasive, but having lobular carcinoma in one breast increases the risk of developing invasive cancer in either breast.

Other types of breast cancer are less common. 

  • Inflammatory breast cancer (IBC) is a rare, aggressive form of breast cancer. In IBC, cancer cells block lymph vessels in the skin, which can cause inflammation, swelling and redness. IBC tumors are not always detected in a breast exam or on a mammogram. This means the cancer has often spread before it is diagnosed
  • HER2 positive breast cancer is a kind of breast cancer with tumors that have higher levels of a protein known as HER2. These tumors tend to grow and spread faster than other breast cancers. Finding out whether a tumor is HER2 positive is important because there are treatments targeted to this cancer type.
  • Triple-negative breast cancers (TNBC) are those that do not have estrogen or progesterone hormone receptors and that are HER2 negative. TNBCs cannot be treated using the therapies that target HER2 cancers, but chemotherapy can be helpful. They occur more often in younger women and in African American women and tend to be more aggressive.
  • Paget’s disease of the breast is a rare type of breast cancer, accounting for 1% to 4% of all cases. Paget’s disease is a noninvasive breast cancer that involves the skin of the nipple and usually the areola (the pigmented circle of skin around the nipple). Most patients with the disease also have ductal carcinoma.

Metastatic Breast Cancer

Metastatic breast cancer is cancer that has spread – or metastasized – to other parts of the body. This happens after cancer cells enter the blood or lymph systems. In most cases, cancer cells die as they are trying to spread. But sometimes, they can form new tumors in other parts of the body. Metastatic cancer cells can also remain inactive after spreading or take many years to grow again. Some of the more common sites for breast cancer to metastasize to are the bone, especially the spine; the brain, which often causes headaches or seizures; and the liver.

Male Breast Cancer

Breast cancer in men is very rare, accounting for less than 1% of all diagnoses. Risk factors for male breast cancer include being older, having high estrogen levels or lower male-hormone levels and having a family history of the disease. Less significant risk factors are radiation exposure, heavy drinking, obesity and having liver disease. 

Stages of Breast Cancer

After a breast cancer diagnosis, doctors will recommend tests to determine what stage the cancer is at. Knowing the breast cancer stage is an important part of determining the best breast cancer treatment options.

Generally speaking, the stages of breast cancer are:

  • Stage 0: This is used to describe in situ cancers, which are also sometimes referred to as pre-cancerous. At this stage, there is no evidence that abnormal or cancerous cells have spread beyond their original location.
  • Stage 1: This stage is divided into 1A and 1B, depending on the size of the tumor and whether it has started to spread to the lymph nodes.
  • Stage 2: In stage 2 (also divided into 2A and 2B), the cancer has grown in size or spread to one or several lymph nodes surrounding the original site.
  • Stage 3: At stages 3A, 3B and 3C, the cancer may have grown in size or spread to multiple lymph nodes, the chest wall or the skin of the breast. Inflammatory breast cancer is usually considered a stage 3B cancer.
  • Stage 4: At this stage, the cancer may have spread beyond the breast and lymph nodes to other organs or sites in the body. This is sometimes also called metastatic breast cancer or advanced breast cancer.
In some cases, even if the cancer is more widespread or larger, it may be considered an earlier-stage cancer. This is because certain factors – for instance, being HER2 negative or estrogen or progesterone receptor positive – may make treatment easier or more effective. 

What Causes Breast Cancer?

Breast cancer develops when cells in the breast tissue begin to grow abnormally and out of control. As these unhealthy cells grow, this leads to the development of a tumor. These tumors can be noncancerous (also referred to as benign) or cancerous (also called malignant). A small number of breast cancers – around 5% to 10% – are related to inherited genetic issues. 

Breast Cancer Risk Factors

Risk factors are things that increase the likelihood of getting breast cancer. Some of the risk factors for breast cancer risk include:

  • A personal or family history of the disease
  • Increased lifetime exposure to estrogen, for instance, due to:
    • Early onset of menstruation (before age 11)
    • Late onset of menopause (after age 55)
    • Taking estrogen and progesterone after menopause
    • Never having given birth or first giving birth after age 30 
  • Having dense breast tissue
  • Obesity
  • Prior radiation therapy to the chest area
  • Consuming alcohol, especially more than two drinks a day
  • Being older than 55 – two-thirds of invasive breast cancers are found in women over age 55.
  • Race and ethnicity – Caucasian women are more likely to be diagnosed with breast cancer, but African American women are more likely to be diagnosed at a younger age (under 45) or to die from the disease.

Is Breast Cancer Genetic?

Breast cancer may be caused by hereditary gene mutations, which are passed on from parents to children. These gene mutations make it more likely that you will develop breast cancer. Research suggests that between 5% and 10% of breast cancer diagnoses are caused by gene mutations.

The most common are mutations to the BRCA1 (breast cancer 1) or BRCA 2 (breast cancer 2) genes. If you have a family history of breast cancer, consider talking to your doctor or a genetic counselor about tests that can help identify whether you have BRCA1 or 2 gene mutations.

Breast Cancer Prevention

There are a few simple ways to reduce your risk of developing breast cancer. These include:

  • Performing regular self-exams to check for lumps or changes to your breasts
  • Following the recommended guidelines for preventative screenings such as mammograms 
  • Maintaining a healthy weight
  • Eating a well-balanced diet
  • Exercising regularly

If you have a very high risk of developing breast cancer, for instance due to a BRCA mutation, breast health specialists may recommend some more significant preventative measures. These include taking estrogen blockers, or surgery to remove the breasts or ovaries. 

What Are the Symptoms of Breast Cancer?

The most common symptoms of breast cancer include:

  • Feeling a lump in the breast area, with or without pain
  • Changes in breast shape or size
  • A dimple or puckering in the breast
  • A nipple turning inward into the breast
  • Nipple discharge other than breast milk, especially if it is bloody
  • Scaly, red, darkened or swollen skin in the breast area
  • Itchy, scaly sores or a rash on the nipple
  • A dimpled, pitted appearance or feeling (similar to an orange peel) in the breast area
  • Swollen or enlarged lymph nodes around the breast area, including the collarbone and armpits

These symptoms can be caused by other conditions. However, if you notice any of these symptoms, you should make an appointment to see your doctor or a breast health specialist.