Invasive breast cancer occurs when cancer cells from inside the milk ducts or lobules break out into nearby breast tissue. Cancer cells can travel from the breast to other parts of the body through the bloodstream or the lymphatic system. Older women are at higher risk. Some women with invasive breast cancer choose to be part of a clinical trial. These trials test new drugs or treatment combinations to see if they are safe and if they work. Invasive Lobular Carcinoma (ILC) is about 10% of invasive breast cancers. ILC starts in the lobules or milk glands and then spreads. With ILC, most women feel a thickening instead of a lump in their breast and Invasive Ductal Carcinoma (IDC) is the most common type, making up about 80%.