Oncology is the science that deals with the study of tumors and cancers.
An oncologist is a person who specializes in the management and care of patients with tumors and cancers. This person may be a physician or non-physician, such as a nurse. The physician may be surgeon or a non-surgeon such as a medical oncologist and a radiation oncologist.
Surgical oncology is the study of tumors and cancers needing surgical treatment, either for diagnosis or for treatment.
A surgical oncologist is a surgeon who specializes in the management and care of patients with tumors and cancers which need surgical intervention of some kind.