A variety of tests are used to diagnose, classify and monitor the progress of cancer in individuals. These tests may be used to diagnose the disease after signs and symptoms have developed, or look for certain cancers before any indications arise.

Screening tests are tests used to detect certain types of cancer before symptoms develop. In their early stages, a number of cancers can be detected with screening tests, including:

• Colorectal cancer
• Prostate cancer
• Breast cancer
• Cervical cancer
• Skin cancer
• Some lung cancers

When patients show signs of cancer, physicians may order a variety of tests to detect the disease, determine the exact type of cancer and monitor the disease’s progression. Additional tests may also be used to determine if the disease has spread to other areas of the body (metastasized).

In order to diagnose cancer, a physician must almost always perform a biopsy. A biopsy is a procedure in which a small sample of tissue is collected and examined under a microscope. Additional tests used to diagnose and classify cancer include laboratory tests (e.g., blood tests, urine tests) and imaging tests (e.g., x-rays, CAT scan).

These tests are important because, in some cases, they allow for early detection of cancer. Finding cancer early is then beneficial because it may improve a patient’s prognosis (outlook). The tests also provide essential information needed by the patient’s cancer care team to make treatment decisions.

This guide focuses on diagnostic tests.