Mastectomy. Artwork depicting a woman crying after having a mastectomy operation. Mastectomy is the surgical removal of the breast, usually performed to treat breast cancer. The amount of breast and surrounding tissue removed depends on various factors. The size and location of the cancerous tumour, how much the cancer has spread and the age and health of the patient are all important considerations. In many cases mastectomy can be avoided and just the tumour will be removed (lumpectomy). When the entire breast has been removed, as depicted here, some form of prosthesis (artificial breast) will be provided. A silicone implant may be inserted later.