Oncology is a branch of medicine that deals with tumors (cancer). Oncology is concerned with the diagnosis of any cancer in a person, therapy (e.g., surgery, chemotherapy, radiotherapy and other modalities), follow-up of cancer patients after successful treatment, palliative care of patients with terminal malignancies and ethical questions surrounding cancer care.

The most important diagnostic tool of oncologists remains the medical history: the character of the complaints and any specific symptoms. Diagnostic methods include biopsy, endoscopy, X-rays, CT scanning, MRI scanning, ultrasound and other radiological techniques.