Within the field of oncology, there are three primary clinical disciplines: medical oncology, surgical oncology, and radiation oncology. A medical oncologist specializes in treating cancer with chemotherapy (the use of drugs to kill cancer cells, usually by stopping the cancer cells’ ability to grow and divide) or other medications, such as targeted therapy and oral (in pill form) chemotherapy. A surgical oncologist specializes in the removal of the tumor and surrounding tissue during an operation. A surgical oncologist also performs biopsies (the removal of a small amount of tissue for examination under a microscope). A radiation oncologist specializes in treating cancer with radiation therapy (the use of high-energy x-rays or other particles to kill cancer cells).