How Is Cancer Diagnosed?

The earlier cancer is diagnosed and treated, the better the chance of its being cured. Some types of cancer -- such as those of the skin, breast, mouth, testicles, prostate, and rectum -- may be detected by routine self-examination or other screening measures before the symptoms become serious. Most cases of cancer are detected and diagnosed after a tumor can be felt or when other symptoms develop. In a few cases cancer is diagnosed incidentally as a result of evaluating or treating other medical conditions.

Diagnosis begins with a thorough physical examination and a complete medical history. Lab studies of blood, urine, and stool can detect abnormalities that may indicate cancer. When a tumor is suspected, imaging tests such as X-rays, computed tomography (CT), magnetic resonance imaging (MRI), ultrasound, and fiberoptic scope examinations help doctors determine its location and size. To confirm the cancer diagnosis, a biopsy is performed: A tissue sample is surgically removed from the suspected malignancy and studied under a microscope to check for cancer cells.