An oncologist is a physician with specialization in diagnosing, treating and providing care to patients who have cancer of any tissue or organ.

The different branches of oncology are:
(1) medical oncology, who treats cancer using chemotherapy
(2) surgical oncology, perform surgical procedures to remove tumour
(3) radiation oncology, provide radiation therapy
(4) gynecologic oncology, treat gynecologic cancer
(5) pediatric oncology, specialist of disease in children
(6) haematologist-oncology, treats blood cancer

A medical oncologist provides treatment of cancer using systematic therapy (chemotherapy, hormone therapy and biological agents), whereas a clinical oncologist uses a combination of chemotherapy and radiotherapy.

Training as an oncologist involves four years of medical school for bachelors degree (MBBS) followed by a residency period and a post-graduate degree in oncology. The post-graduation degree may be MD in medicine/paediatrics, with a DM in medical oncology or MD in radiotherapy.

A surgical oncologist, who has got training at surgical procedures can perform surgery to remove tumours.