Oncologist Email Lists:  Cancer science is known as oncology because it comes from the Greek word "onkos", which means "tumor" or "mass." Hence, oncologists are medical doctors who specialize in diagnosing, preventing, and treating cancer. Within the Oncology profession, there are four types of physicians: medical oncologists (chemotherapy or medications), surgical oncologists (surgical procedures for various tumors), radiation oncologists (megavoltage X-rays or radionuclides), and pediatric oncologists (physicians specializing in childhood cancer).).