Inflammatory breast cancer accounts for 1 to 5 percent of all breast cancers diagnosed in the United States. Most inflammatory breast cancers are invasive ductal carcinomas, which means they developed from cells that line the milk ducts of the breast and then spread beyond the ducts.
Inflammatory breast cancer progresses rapidly, often in a matter of weeks or months. Inflammatory breast cancer is either stage III or IV at diagnosis, depending on whether cancer cells have spread only to nearby lymph nodes or to other tissues as well. It is not commonly picked up by a mammogram.