Breast cancer occurs when normal cells in the breast undergo changes in their molecular characteristics, allowing them to grow and multiply uncontrollably. Excluding skin cancers, breast cancer is the most common type of cancer in women, affecting approximately 12% of women over the course of their lifetime.
Breast cancer is described based on the type of breast tissue where the tumor originates. For example, cancers that begin in the breast ducts are called ductal cancers and those in the lobules (glands) are lobular cancers.
Breast cancer typically does not cause symptoms in the early stages and is often detected with screening mammograms. Treatments depend on the cancer stage and type, and may include surgery, chemotherapy, hormonal therapy, biological therapy, and radiation therapy.
While breast cancer is rare in men, the disease can affect men too. Men can also have breast lumps and should get a prompt medical evaluation for any lump or change in the appearance of their chest or breast area.
Breast cancer is usually painless during its early stages, but growths can stretch the skin and breast tissue, causing discomfort or pain. The pain can be anywhere in the breast or it may occur in the nipple.
To check for lumps, perform monthly mid-cycle self-checks (about two weeks after your period). Screening mammograms are recommended yearly for women over the age of 45, and sometimes younger for those considered high risk. Doctors may do breast examinations, take a biopsy (sample of breast tissue), or may recommend genetic testing, such as for BRCA gene mutations linked to breast cancer.
Seek medical attention if you feel or notice a lump in your breast or if you have any breast or nipple pain, swelling in the armpit (lymph nodes), persistent tenderness, an inverted or retracted nipple, or a change in breast size or shape. Additional things to look for are breast discoloration, scaly or pitted skin, and clear or bloody nipple discharge.
Cells with mutations that allow them to grow uncontrollably and continue to divide without stopping. They are able to invade nearby tissues and spread throughout the body, often evading the immune system.
Intraductal carcinoma (also called ductal carcinoma in situ) is when there is cancer in the milk ducts that hasn’t yet spread to other tissue. This is considered an early form of cancer, a stage zero, that isn’t yet invasive.
Invasive ductal carcinoma (IDC), which is sometimes called infiltrating ductal carcinoma, is a cancer in the milk ducts of the breast that has invaded nearby breast tissue. It is the most common type of breast cancer and approximately 80% of invasive breast cancers are invasive ductal carcinomas.
Small glands that are part of the immune system. Lymph nodes are distributed along lymphatic vessels that transport lymph. Lymph is a fluid from cells and tissues that contain a variety of substances and white blood cells that fight infections. With solid tumor cancers, cancer cells often travel to lymph nodes before other areas. Lymph nodes are a common site for spread in breast cancer.
National Cancer Institute. Breast Cancer Risk in American Women. Updated October 3, 2019.
Centers for Disease Control and Prevention. How Is Breast Cancer Treated? Updated September 14, 2020.
American Cancer Society. Frequently Asked Questions About the American Cancer Society’s Breast Cancer Screening Guideline. Updated January 24, 2019.
American Cancer Society. Invasive breast cancer (IDC/ILC). Updated September 20, 2019.
American Cancer Society. What Is Breast Cancer? Updated September 18, 2019.