National Breast Cancer Foundation, Inc.

Breast Cancer is caused by cells that start to grow rapidly and invade nearby tissues. When large collections of these tissue gather, they are called tumors, but not all tumors can spread and are therefore not considered cancerous.


Breast cancer tissues usually come from the ducts or glands, but any types of tissue in the breast can form cancer. It is the most common malignancy affecting women in North American and Europe and every woman is at risk. Even if you do not have a family history of breast cancer, you are still at risk. So it is incredibly important to screen for tumors with mammograms, especially since it can take months to years for a tumor to get large enough to feel in the breast.