Each month, a woman's breasts go through temporary changes associated with menstruation and a lump may form. While the vast majority of these growths are not breast cancer, any lump should be examined immediately.
Breast lumps are most common in the lobules -- small sacs that produce milk -- or the ducts that carry milk to the nipple. But they occasionally start in other tissue. The two main categories of breast cancer are lobular and ductal carcinomas.
Purpose of This Summary
This PDQ cancer information summary for health professionals provides comprehensive, peer-reviewed, evidence-based information about the treatment of breast cancer and pregnancy. It is intended as a resource to inform and assist clinicians who care for cancer patients. It does not provide formal guidelines or recommendations for making health care decisions.
Reviewers and Updates
This summary is reviewed regularly and updated as necessary by the PDQ Adult Treatment...
Breast cancer usually begins with the formation of a small, confined tumor. Some tumors are benign, meaning they do not invade other tissue; others are malignant, or cancerous. Malignant tumors have the potential to metastasize, or spread. Once such a tumor grows to a certain size, it is more likely to shed cells that spread to other parts of the body through the bloodstream and lymphatic system. Different types of breast cancer grow and spread at different rates; some take years to spread beyond the breast, while others move quickly.
Men can get breast cancer, too, but breast cancer is about 100 times less common in men. Among women, breast cancer is the most common cancer and the second leading cause of cancer deaths after lung cancer.
If eight women were to live to be at least 90, one of them would be expected to develop the disease at some point during her life. Two-thirds of women with breast cancer are over 50.
Fortunately, breast cancer is very treatable if detected early. Localized tumors can usually be treated successfully before the cancer spreads; and in nine in 10 cases, the woman will live at least another five years.
Once the cancer begins to spread, getting rid of it completely is more difficult, although treatment can often control the disease for years.