Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread to other parts of the body. Oncology is the study of cancer. An oncologist is a doctor who treats cancer and provides medical care for a person diagnosed with cancer. The field of oncology has three major areas: medical, surgical, and radiation. … A surgical oncologist removes the tumor and nearby tissue during surgery.