If i choose breast-sparing surgery, how much of the breast has to be taken out?

It depends: It depends on the size of your tumor. The entire tumor needs to be removed along with a rim of normal tissue. Ask your surgeon to show you how much of your breast tissue will be removed.

Clear margins.: The goal of a lumpectomy is to remove all of the cancer as well as a rim of normal breast tissue; this is described as "clear margins" by the pathologists. Therefore, the amount of tissue removed is dependent on the size of the cancer. While our first priority is always "cure", we have become adept at performing this operation following principles learned from our plastic surgery colleagues.