How is cancer diagnosed?
Some cancers are diagnosed during routine screening examinations. These are usually tests that are routinely done at a certain age. Many cancers are discovered when you present to your health care professional with specific symptoms.
A physical exam and medical history, especially the history of symptoms, are the first steps in diagnosing cancer. In many instances, the medical caregiver will order a number of tests, most of which will be determined by the type of cancer and where it is suspected to be located in or on the person's body. In addition, most caregivers will order a complete blood count, electrolyte levels and, in some cases, other blood studies that may give additional information.
Imaging studies are commonly used to help physicians detect abnormalities in the body that may be cancer. X-rays, CT and MRI scans, and ultrasound are common tools used to examine the body. Other tests such as endoscopy, which with variations in the equipment used, can allow visualization of tissues in the intestinal tract, throat, and bronchi that may be cancerous. In areas that cannot be well visualized (inside bones or some lymph nodes, for example), radionuclide scanning is often used. The test involves ingestion or IV injection of a weakly radioactive substance that can be concentrated and detected in abnormal tissue.
The preceding tests can be very good at localizing abnormalities in the body; many clinicians consider that some of the tests provide presumptive evidence for the diagnosis of cancer. However, in virtually all patients, the definitive diagnosis of cancer is based on the examination of a tissue sample taken in a procedure called a biopsy from the tissue that may be cancerous, and then analyzed by a pathologist. Some biopsy samples are relatively simple to procure (for example, skin biopsy or intestinal tissue biopsy done with a device called an endoscope equipped with a biopsy attachment). Other biopsies may require as little as a carefully guided needle, or as much as a surgery (for example, brain tissue or lymph node biopsy). In some instances, the surgery to diagnose the cancer may result in a cure if all of the cancerous tissue is removed at the time of biopsy.
The biopsy can provide more than the definitive diagnosis of cancer; it can identify the cancer type (for example, the type of tissue found may indicate that the sample is from a primary [started there] or metastatic type of brain cancer [spread from another primary tumor arising elsewhere in the body]) and thereby help to stage the cancer. The stage, or cancer staging, is a way for clinicians and researchers to estimate how extensive the cancer is in the patient's body.
Is the cancer that has been found localized to its site of origin, or is it spread from that site to other tissues? A localized cancer is said to be at an early stage, while one which has spread is at and advanced stage. The following section describes the general staging methods for cancers.