How Can Cancer Be Diagnosed?

cancer cells
Diagnostic tests can confirm or eliminate the presence of cancer

Cancer testing for a patient requires a thorough medical history and physical examination along with multiple diagnostic tests. Diagnostic tests can confirm or eliminate the presence of disease and monitor the disease process. Diagnostic testing for cancer includes:

  • Laboratory tests (including tests for tumor markers)
  • Imaging tests
  • Endoscopic examination
  • Genetic testing
  • Tumor biopsy

What tests are used to detect cancer?

Laboratory tests

If your physician suspects cancer during physical examination or while taking a medical history, they may order certain cancer blood tests to guide the diagnosis. Blood tests usually don’t detect cancer or benign tumors. However, blood tests can give a general idea about the functioning of your organs and if they have been affected by cancer. 

High or low levels of certain components in your blood could be a sign of cancer. Lab tests for blood, urine or other body fluids that measure these components can help your doctor identify cancer. Some of these lab tests include:

Abnormal lab results do not always mean cancer.

Different types of tumor markers for cancer diagnosis chart
Carcinoembryonic antigen (CEA) Medullary thyroid cancer (MTC), testicular cancer, ovarian cancer, colon cancer
Calcitonin Medullary thyroid cancer (MTC)
Thyroglobulin All types of thyroid cancer
Alpha-fetoprotein (AFP) Testicular cancer, liver cancer
Human chorionic gonadotrophin (HCG) Choriocarcinoma, testicular cancers
PD-L1 protein Lung cancers
Cancer antigen-125 (CA-125) Ovarian cancer
Circulating tumor cells Cancers of the digestive tract

Imaging tests

Imaging tests take images of body structures and organs. Imaging can help diagnose cancer by:

  • Detecting tumors and other abnormalities.
  • Determining the extent of the disease.
  • Evaluate the effectiveness of treatment.

Some imaging tests include:

  • Ultrasound: Uses high-energy sound waves that echo tissues in the body to create pictures of the organs and structures. An ultrasound, especially a Doppler ultrasound, is often used to diagnose cancer of the testis.
  • Computed tomography (CT) scan: Uses an X-ray machine linked to the computer to create three-dimensional (3-D) images of the organs and structure of the body. A CT is often sensitive for cancer diagnosis of internal organs, such as lungs, ovaries and kidneys.
  • Magnetic resonance imaging (MRI) scan: Uses a powerful magnet or radio waves to create images of the body in slices. These slices are used to create detailed images of the organs and structure, which helps differentiate healthy and unhealthy tissues. An MRI can often successfully detect the tumors of the brain, bone and heart.
  • Nuclear scan: Uses radioactive material to create images of the organs and structures. Cancers in the active tissues, such as the thyroid, are often identified in this scan.
  • Bone scan: A type of nuclear scan that identifies abnormal areas in bone. A bone scan can detect advanced cancer that has spread to the bones.
  • Positron emission tomography (PET) scan: A type of nuclear scan that creates 3-D images of the area inside the body where glucose is absorbed.
  • X-ray: Uses a low dose of radiation to create images of the organs and structures in the body. Cancers of bone are identified effectively by X-ray imaging.

Tumor biopsy

A biopsy is a diagnostic procedure to confirm whether the tissue is malignant or benign. In a tumor biopsy, the physician removes tissues or cells from the body for examination under a microscope. 

The most common types of biopsies include:

Endoscopic examination

The most commonly used endoscopic examination includes:

Genetic testing

Testing for mutations in genes that increases the risk of cancer is important for better management of cancer. These tests are highly specialized. They test for the mutations in genes: BRCA 1 and BRCA 2, MEN 1 and RET, APC, etc.

National Cancer Institute. How Cancer Is Diagnosed. National Institutes of Health.

Mayo Clinic. Cancer Blood Tests: Lab Tests Used in Cancer Diagnosis.