Breast cancer occurs when cells within the breast grow and multiply abnormally. This process can cause a tumor to form. In many cases, the tumor is benign (noncancerous). In the case of a malignant (cancerous) tumor, the cells continue dividing uncontrollably and can invade nearby tissues and potentially metastasize (spread) to other parts of your body. These tumors are known as invasive tumors. There is also a form of noninvasive breast cancer called ductal carcinoma in situ (DCIS); some DCIS tumors may become invasive.
Although it’s much less common, breast cancer can also occur in men. Learn more about male breast cancer.
Just because you have the following symptoms doesn’t always mean you have breast cancer, but you should see a doctor right away if they occur:
- a physical change in the breast, such as a lump or a thickening
- an inflammatory change, such as redness or hardening of the breast
It’s also possible that even though your breast feels normal, a screening test shows an abnormality.