Preliminary diagnosis identifies a suspicious mass or other change in the body that requires further investigation. Some symptoms must be evaluated with special X rays and other advanced imaging techniques. One X-ray technique, called computed tomography or CT scan, can reveal suspicious masses in such internal organs as the brain and the lungs. A technique called magnetic resonance imaging (MRI) uses magnetic fields and radio waves to produce images of internal organs. These imaging techniques allow physicians to determine the exact location, size, and shape of cancer tumors and determine whether the cancer has spread.

Conclusive diagnosis. The various methods of preliminary diagnosis may reveal the presence of a tumor. But not all tumors are cancerous. Most lumps in the breast, for example, are benign (noncancerous). Doctors need to perform a test called a biopsy to make a definite diagnosis of cancer. In a biopsy, doctors remove a small piece of tissue from the tumor. In suspected cases of leukemia, they take a blood sample or remove tissue from a blood-forming organ. Experts then examine the tissue under a microscope to check for cancer cells.

Staging. Physicians use a process called staging to describe how a particular cancer in a patient has advanced. Staging is important in helping physicians decide which treatments are most likely to be successful in treating the cancer. The most common staging method is known as the TNM system. This system describes the tumor (T), whether the cancer has invaded lymph nodes (N), and whether there are any metastases (M). Physicians determine the staging level through physical examination, X rays, CT scans, and other specialized tests.

Since each type of cancer is different, there are different staging categories for each cancer. If cancer is discovered in the early stages, the cancer treatment may be successful. Advanced stage cancers are more difficult to treat. If tests show that the cancer has spread, patients may need to undergo additional treatments.