Overview
         Oncology is a specialty within medicine that deals with the diagnosis and treatment of cancer, a disease that can affect many different tissues. The way in which cancer is treated depends on both the location of the cancer, as well as how fast it is growing.

Malignant Vs. Benign
         One of the important parts of oncology is being able to distinguish between malignant and benign tumors. Benign tumors are abnormal growths that are rarely life-threatening and can often be surgically removed without growing back, the National Cancer Institute explains. As such, benign tumors are not considered to be cancerous. Malignant tumors, on the other hand, can grow back after surgical removal and also have the ability to spread to other tissues. These types of tumors, which are considered cancerous, can even spread to distant locations within the body via a process known as metastasis.

Genetics
         Oncology also deals with the genetic changes that lead to cancer, which begins in normal cells that develop genetic mutations. Sometimes these genetic mutations are inherited, the American Cancer Society explains. Most of the time, however, the genetic mutations occur over a period of time. These mutations can cause the cells to grow uncontrollably and to develop the ability to invade surrounding tissue. Although these genetic changes happen at random, certain factors, such as cigarette smoking or excessive exposure to sunlight, can increase the likelihood that dangerous genetic mutations will occur.

Diagnosis
         Several tests can be used to detect the presence of a tumor, the National Cancer Institute explains. Many of these are imaging tests, such as X-rays, CT scans and MRIs, which can detect the presence of large tissue growths. Often, to make a definitive diagnosis of cancer, a tissue biopsy is needed. Tissue biopsies require that a surgeon take a small amount of tissue from a patient's tumor. The tissue can then be analyzed under a microscope to examine the cells. Cancer cells typically look different from normal cells on a microscopic level; the degree to which the cancer cells appear abnormal can be an important prognostic factor and can guide treatment.

When to See Oncologist
         Several symptoms may necessitate the expertise of a physician trained in oncology, the American Cancer Society explains. Unexplained weight loss, fatigue, chronic pain and a fever are symptoms that many different kinds of cancer can cause. The presence of unusual lumps in the body or the appearance of blood in the stool, stomach or lungs may also be a sign of cancer and requires more extensive follow-up. Problems with swallowing, breathing, coughing, indigestion and bowel movements may also be reason enough to consult an oncologist to determine if the symptoms are due to cancer.

Treatment
         A critical aspect of oncology is the treatment of cancer. Common therapies for cancer are surgery, chemotherapy and radiation treatment, the Journal of the American Medical Association (JAMA) explains. The goal of surgery is to remove as much of the cancerous material as possible. Chemotherapy and radiation, which are often used along with surgery, work to poison and kill the cancer cells. Chemotherapy accomplishes this via the administration of chemicals that kill the rapidly dividing cancer cells. Radiation, on the other hand, uses high-energy X-ray beams that are focused on the cancer cells, resulting in cellular damage and death of cancerous cells.