Breast cancer is a malignant tumour that has developed from cells of the breast. A malignant tumour is a group of cancer cells that may invade surrounding tissues or spread (metastasize) to distant areas of the body. The disease occurs almost entirely in women, but men can get it as well. The main types of breast cancer are ductal carcinoma in situ, invasive ductal carcinoma, lobular carcinoma in situ, invasive lobular carcinoma, medullary carcinoma, and Paget's disease of the nipple. About 1 of 8 women will get it in their lifetime. This book presents state-of-the-art research in this fast-moving field.