What is Breast Cancer?

In a healthy body, natural systems control the creation, growth and death of cells. But when these systems malfunction, more cell growth than death can occur. The result is a mass of tissue we call a malignant tumor—or cancer. And when this process takes place in the breast, it’s breast cancer. Tumors in the breast tend to grow slowly; by the time a lump is large enough to feel, it may have been growing for as long as 10 years. Some tumors, however, are aggressive and grow much faster. 

Did you know? 

50 to 75% of breast cancers begin in the milk ducts. 10 to 15% begin in the lobules. A few begin in other breast tissues.

Non-invasive Breast Cancer 

Non-invasive breast cancer (also known as ductal carcinoma in situ or DCIS) occurs when abnormal cells grow inside the milk ducts but have not spread to nearby tissue or beyond. This may also be referred to as “pre-invasive breast carcinoma.” Although the abnormal cells have not spread to tissues outside the ducts, they can develop into invasive breast cancer. Learn more

Invasive Breast Cancer

Invasive breast cancer is when abnormal cells break out of the milk ducts or lobules and move into nearby breast tissue. Cancer cells can travel from the breast to other parts of the body through the blood stream or the lymphatic system. And they may travel early in the process when the tumor is small or later when the tumor is large. 

The lymph nodes in the underarm area (the axillary lymph nodes) are the first place that breast cancer is likely to spread. In advanced stages, breast cancer cells may spread to other parts of the body like the liver, lungs, bones and brain (in a process called metastasis). There, the breast cancer cells may again begin to divide too quickly and form new tumors. Learn more

Stage IV Breast Cancer 

Stage IV breast cancer (also known as metastatic or advanced breast cancer) has spread beyond the breast to other parts of the body, most often the bones, lungs, liver or brain. Some women have stage IV when they are first diagnosed but this is not common in the United States. More commonly, metastatic breast cancer arises months or years after a person has completed treatment for early or locally advanced breast cancer (stage I, II, or III.) Learn more

Other Forms of Breast Cancer 

Though they are not specific types of tumors, there are some special forms of breast cancer. These include inflammatory breast cancer (IBC), Paget disease of the breast or nipple, and metaplastic breast cancer. Learn more

Diagnosing and Treating Breast Cancer

 Differences in breast cancer type, tumor, stage, and other factors affect treatment and prognosis. Because of this, it’s important to understand the details of your diagnosis before choosing a treatment path. 

If you’re ready to learn how breast cancer is diagnosed and what you can expect to learn from diagnostic reports, get started here.

Updated 03/20/14