ILC stands for Invasive Lobular Carcinoma, which is a type of breast cancer that starts in the milk-producing gland or lobes of the breast. It is the second most common form of invasive breast cancer, accounting for 10-15% of diagnosed cases in the United States. ILC is made up of small cancer cells that invade the stroma, the fatty tissue surrounding the lobules. It can be difficult to detect on a mammogram and can grow into lines that are difficult to detect on physical exams. Some studies suggest that hormone replacement therapy increases the risk of these cancers. Symptoms of ILC include an area of thickening, swelling, or fullness in the breast, a nipple that turns inward, and a change in the texture of the breast skin. ILC can only be diagnosed by a biopsy, which is a procedure during which a sample of cells is removed from the breast and examined under a microscope, looking for the presence of cancer cells. Treatment for ILC may include surgery, radiation therapy, chemotherapy, and hormone therapy.