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Melanoma: Tests After Diagnosis

Once you’re diagnosed with melanoma, you may need more tests. These help your doctor learn more about your cancer, so a treatment plan can be made. The tests may include one or more of these:

  • Sentinel lymph node biopsy

  • Fine needle aspiration (FNA) biopsy

  • Computed tomography (CT) scan

  • Magnetic resonance imaging (MRI)

  • Positron-emission tomography (PET) scan

  • Blood tests

  • Chest X-ray

Sentinel lymph node biopsy

If you have a thick melanoma or one with more signs of disease, you may need a sentinel lymph node biopsy. This procedure removes nearby lymph nodes to check for cancer cells. It’s done because melanoma often spreads first to the lymph nodes.

In a group of lymph nodes, cancer is most likely to go to one or two lymph nodes first. These lymph nodes are called sentinel lymph nodes. During the procedure, a surgeon removes a sentinel lymph node. It’s then examined for cancer cells. If no cancer is found, the other lymph nodes in the group can be left in place. Results of a sentinel lymph node biopsy help your doctor determine what treatment you may need.

During a sentinel node biopsy:

  • The process starts with lymph node mapping. This is a way to find out which lymph node nearest to the melanoma is the sentinel node. The doctor injects a small amount of radioactive tracer into your skin near the melanoma site. It takes about an hour for the tracer to follow the same path as a melanoma cell would to the nearest lymph node.

  • The doctor uses a special device that detects radioactivity called a Geiger counter. This helps to show where the cancer cells are most likely to go. The doctor also may inject a blue dye, which travels to the lymph nodes. The lymph node that shows up with radioactivity is called the sentinel lymph node. 

  • The doctor makes a small incision to remove this lymph node.

  • Right after removing the lymph node, your doctor may do a wide local excision. This is a surgery to remove more tissue around the melanoma. This can help prevent melanoma from recurring.

  • The sentinel lymph node is examined for cancer cells.

  • If it does not have melanoma cells, you may not need additional tests. The doctor will leave the other lymph nodes in place.

  • If the removed lymph node has melanoma cells, your doctor will remove all the lymph nodes in that region. This is called lymph node dissection. You might also need imaging tests, such as computed tomography (CT scans), magnetic resonance imaging (MRI), and a positron emission tomography (PET) scan, as well as blood tests.

Fine needle aspiration (FNA) biopsy

If your doctor thinks the cancer has spread, you may have a fine needle aspiration (FNA) biopsy. This is a procedure used to biopsy nearby lymph nodes or organs. You may first get a local anesthetic to numb the area. The test rarely causes much discomfort and leaves no scar. The doctor uses a syringe with a small needle to remove small tissue from the node or organ. The doctor may use imaging tools such as a computed tomography (CT) scan or ultrasound during the biopsy. This is to help guide the needle to the right place.

Computed tomography (CT) scan

This test helps your doctor see where the melanoma is located and if it has spread to other parts of your body. It is helpful for finding melanoma cells in the chest, abdomen, and pelvis.

A CT scan uses a series of X-rays and a computer to create detailed images of the inside of the body. During the test, you lie still on a table as it slowly slides through the center of the CT scanner. The scanner directs a beam of X-rays at your body. A CT scan is painless. You may be asked to hold your breath one or more times during the scan. You may need to drink a contrast medium or receive it by an intravenous (IV) injection.

You may be asked not to eat until a second set of pictures is taken in a few hours. The dye allows your doctor to better see lymph nodes and other tissues. The substance will gradually pass through your system and exit through your bowel movements. Some people have a temporary warm feeling (flushing) just after the injection. Tell your doctor if you have ever had a reaction to contrast material in the past, such as hives or trouble breathing. Tell your doctor if you have these reactions during the test.

Magnetic resonance imaging (MRI)

This test is helpful in looking at your brain and spinal cord. MRI may also be used if the results of an X-ray or CT scan aren’t clear. MRIs use radio waves, magnets, and a computer to make detailed images of the inside of the body.

For this test, you lie still on a table as it passes through a tube-like scanner. If you are not comfortable in small spaces, you may be given a sedative before the test. The scanner directs a beam of radio waves at the area to examine. You may need more than one set of images. Each one may take 2 to 15 minutes. This test is painless. It may last an hour or more. The machine is loud during the test. You can ask for earplugs or headphones with music.

Positron-emission tomography (PET) scan

A PET scan can examine your entire body. For this test, you either swallow or are injected with a mildly radioactive substance, usually a form of glucose. The PET scan will show where in your body the glucose is being used the most. This helps find active cells that are dividing quickly, such as cancer.

You’ll lie still on a table that is pushed into the PET scanner. It will rotate around you and take pictures. Other than the injection, a PET scan is painless and noninvasive. Some people are sensitive to the substance, and may have nausea, a headache, or vomiting. Some newer machines can do PET and CT scans at the same time, so areas that show up on the PET scan can be compared to the more detailed image of the CT scan. 

Blood tests

Your doctor may advise a lactate dehydrogenase (LDH) test. LDH is an enzyme in the blood. Sometimes LDH blood levels are high when many cancer cells are present, or when the liver has been damaged by cancer. This test can be helpful in showing if cancer has spread.

Chest X-ray

A chest X-ray is done to see if there are any changes in your lungs. This may show that the melanoma has spread. An X-ray uses a small amount of radiation to make an image of organs and bones inside the body. The test can spot enlarged lymph nodes in your chest area. This test takes a few minutes, and causes no pain.

Working with your health care provider

Your doctor will talk with you about which tests you’ll have. Make sure to prepare for the tests as instructed. Ask questions and talk about any concerns you have.

Online Medical Reviewer: Alteri, Rick, MD
Online Medical Reviewer: Foster, Sara M., RN, MPH
Last Review Date: 12/20/2014
© 2013 The StayWell Company, LLC. 780 Township Line Road, Yardley, PA 19067. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare provider's instructions.