Oncology is the branch of medicine dealing with tumors (cancer). A medical professional who practices oncology is an oncologist. The term originates from the Greek onkos (ονκος), meaning bulk, mass, or tumor, and the suffix -logy, meaning "study of".

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
• Ethical questions surrounding cancer care
• Screening efforts:
• of populations, or
• of the relatives of patients (in types of cancer that are thought to have a hereditary basis, such as breast cancer)

Diagnosis

The most important diagnostic tool remains the medical history: the character of the complaints and any specific symptoms (fatigue, weight loss, unexplained anemia, fever of unknown origin, paraneoplastic phenomena and other signs). Often a physical examination will reveal the location of a malignancy.

Diagnostic methods include:

• Biopsy, either incisional or excisional;
• Endoscopy, either upper or lower gastrointestinal, bronchoscopy, or nasendoscopy;
• X-rays, CT scanning, MRI scanning, ultrasound and other radiological techniques;
• Scintigraphy, Single Photon Emission Computed Tomography, Positron emission tomography and other methods of nuclear medicine;
• Blood tests, including Tumor markers, which can increase the suspicion of certain types of tumors or even be pathognomonic of a particular disease.

Apart from in diagnosis, these modalities (especially imaging by CT scanning) are often used to determine operability, i.e. whether it is surgically possible to remove a tumor in its entirety.

Generally, a "tissue diagnosis" (from a biopsy) is considered essential for the proper identification of cancer. When this is not possible, "empirical therapy" (without an exact diagnosis) may be given, based on the available evidence (e.g. history, x-rays and scans.)

Occasionally, a metastatic lump or pathological lymph node is found (typically in the neck) for which a primary tumor cannot be found. This situation is referred to as "carcinoma of unknown primary", and again, treatment is empirical based on past experience of the most likely origin.

Therapy

It depends completely on the nature of the tumor identified what kind of therapeutical intervention will be necessary. Certain disorders will require immediate admission and chemotherapy (such as ALL or AML), while others will be followed up with regular physical examination and blood tests. A detailed discussion of treatment options according to the type of cancer is at the National Cancer Institute website with sections on adult cancers, pediatric cancers, and supportive care. There is also a section on complementary and alternative methods of treatment.