Diagnosis

Doctors use many tests to diagnose cancer and determine if it has metastasized (spread). Some tests may also determine which treatments may be the most effective. For melanoma, a biopsy is the only way to make a definitive diagnosis of cancer. If a biopsy is not possible, the doctor may suggest other tests that will help make a diagnosis. Imaging tests may be used to find out whether the cancer has metastasized. Your doctor may consider these factors when choosing a diagnostic test:

• Age and medical condition
  
  
• The type of cancer suspected
  
  
• Severity of symptoms
  
  
• Previous test results

If a person shows signs of melanoma, the doctor will take a complete medical history, noting the symptoms and risk factors. The following tests may be used to diagnose melanoma and/or determine if or where the disease has spread:

Physical examination. A physical examination includes a thorough examination of the person’s skin for lesions.

Biopsy. A biopsy is the removal (usually performed with a local anesthetic to numb the area) of a small amount of tissue for examination under a microscope. The suspect lesion is removed using techniques that preserve the entire lesion so that the thickness of the potential cancer and its margin (healthy tissue around the lesion that is removed to make sure no cancer cells remain) can be carefully examined. The tissue sample is analyzed by a pathologist (a doctor who specializes in interpreting laboratory tests and evaluating cells, tissues, and organs to diagnose disease), who determines if it is a melanoma.

Sentinel lymph node biopsy. This type of biopsy is a surgical procedure and is used to determine if cancer cells have spread to the regional lymph nodes (lymph nodes near the site of the cancer). For a more detailed description of the surgery, read the Treatment section.

X-ray. An x-ray is a picture of the inside of the body. For instance, a chest x-ray can help doctors determine if the cancer has spread to the lungs.

Blood tests. The patient’s blood may be tested to help determine if the cancer has spread.

Occasionally, the following tests may be performed to diagnose melanoma and/or help determine if or where the cancer has spread:

Ultrasound. An ultrasound uses sound waves to create pictures of the internal organs, including collections of lymph nodes (called basins) and soft tissue.

Computed tomography (CT or CAT) scan. A CT scan creates a three-dimensional picture of the inside of the body with an x-ray machine. A computer then combines these images into a detailed, cross-sectional view that shows any abnormalities or tumors. Sometimes, a contrast medium (a special dye) is injected into a patient’s vein to provide better detail.

Magnetic resonance imaging (MRI). An MRI uses magnetic fields, not x-rays, to produce detailed images of the body. A contrast medium may be injected into a patient’s vein to create a clearer picture.

Positron emission tomography (PET) scan. A PET scan is a way to create pictures of organs and tissues inside the body. A small amount of a radioactive substance is injected into a patient’s body and absorbed by the organs or tissues being studied. This substance gives off energy that is detected by a scanner, which produces the images.

Learn more about what to expect when having common tests, procedures, and scans.

Find out more about common terms used during a diagnosis of cancer.