Final answer:
Peter's doctor refers him to an oncologist because he thinks Peter has cancer. The oncologist will evaluate Peter's symptoms, perform diagnostic tests, and develop a treatment plan based on the specific type and stage of cancer.
Step-by-step explanation:
Peter's doctor refers him to an oncologist because he thinks Peter has cancer, which is a disease characterized by the uncontrolled growth of abnormal cells in the body. There are various types of cancer, including pancreatic cancer, brain tumors, breast cancer, cervical cancer, metastatic prostate cancer, lymphoma, colorectal cancer, kidney cancer, lung cancer, and melanoma. The oncologist will evaluate Peter's symptoms, perform diagnostic tests, and develop a treatment plan based on the specific type and stage of cancer.