What Is Breast Cancer?
Breast cancer is a disease in which cells in the breast grow in an uncontrolled way. While breast cancer most often affects women and people assigned female at birth, men can also develop the disease. Breast cancer usually begins in the ducts or lobules of the breast and may appear as a lump, an abnormal area on imaging, or changes in the breast or skin.
Types of Breast Cancer
Breast cancers are classified based on where they start and how the cancer cells behave.
Non-Invasive Conditions
- Ductal Carcinoma In Situ (DCIS)
DCIS is a non-invasive condition in which abnormal cells are confined to the milk ducts and have not spread into surrounding breast tissue. DCIS often does not cause symptoms and is most commonly detected on routine mammography. - Lobular Carcinoma In Situ (LCIS)
LCIS is not considered a true cancer. It refers to abnormal cells found in the lobules (milk-producing glands) of the breast and indicates a higher future risk of developing invasive breast cancer in either breast.
Invasive Breast Cancers
- Invasive Ductal Carcinoma (IDC)
IDC is the most common type of breast cancer, accounting for approximately 80% of cases. It begins in the milk ducts and spreads into surrounding breast tissue, with the potential to spread to lymph nodes or other parts of the body. - Invasive Lobular Carcinoma (ILC)
ILC begins in the lobules and spreads into nearby breast tissue. It accounts for about 10% of breast cancer diagnoses and can be more difficult to detect on imaging.
Breast Cancer Subtypes
Some breast cancers are further classified based on receptors found on the cancer cells, which help guide treatment:
- Hormone Receptor–Positive Breast Cancer
These cancers grow in response to estrogen and/or progesterone and are often treated with hormone-blocking therapies. - HER2-Positive Breast Cancer
HER2-positive cancers have excess HER2 protein, causing them to grow and spread more quickly. Targeted therapies have significantly improved outcomes for these patients. - Triple-Negative Breast Cancer (TNBC)
TNBC lacks estrogen, progesterone, and HER2 receptors. It tends to grow and spread more quickly and is treated primarily with chemotherapy and, in some cases, immunotherapy. - Inflammatory Breast Cancer (IBC)
IBC is a rare but aggressive form of breast cancer that often causes redness, swelling, warmth, and skin changes rather than a distinct lump.
Risk Factors
The exact cause of breast cancer is not known, but several risk factors increase the likelihood of developing the disease:
- Sex
Being a woman, or a person assigned female at birth, is one of the most important risk factors for developing breast cancer. - Family History
Women with close relatives who have been diagnosed with breast cancer – especially mothers, sisters, or daughters – have a higher risk of developing the disease. - Genetic Factors
Inheritance of gene mutations such as BRCA1 and BRCA2 significantly raises the risk. - Age
Breast Cancer risk increases with age; most cases are diagnosed in women over 50. - Hormone Replacement Therapy (HRT)
Hormone Replacement Therapy (HRT), also called estrogen replacement therapy or menopausal and post-menopausal therapy, can be effective in treating menopausal symptoms. However, some types of HRT can increase breast cancer risk. - Lifestyle Factors
Alcohol consumption, obesity, and lack of physical activity are known to elevate the risk. - Reproductive History
Early menstruation before age 12, late menopause after age 55, having your first child at an older age, or never having given birth can also raise breast cancer risk.
Prevention
Not all breast cancers can be prevented, but risk may be reduced by:
- Maintaining a healthy weight
- Staying physically active
- Limiting alcohol consumption
- Attending regular breast cancer screenings
Early detection through screening leads to better outcomes. The GW Cancer Center’s Breast Cancer Program offers expert, compassionate care for patients with breast concerns, from screening through survivorship.