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Tests that Help Evaluate Melanoma
Your doctor may request other tests to learn more about your specific type of melanoma. The tests may also tell how widespread the cancer is. Along with previous exams and biopsies, these tests can help your doctor know the stage and prognosis of your disease. They can also help your doctor decide on the best care for you. You may need one or more of these tests. If the melanoma is thin and does not have concerning features, you may not need other tests.
Thicker melanomas or those with concerning features may require a procedure called lymphoscintigram and sentinel lymph node biopsy.
Lymphoscintigram with sentinel lymph node biopsy
Because melanoma commonly spreads first to the lymph nodes, your doctor may advise that you have surgery to remove your lymph nodes so they can be checked for cancer. Within any 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. A surgeon removes a sentinel lymph node and examines it. If no cancer is present there, the other lymph nodes in the group are very unlikely to contain cancer and can be left in place. Results of a sentinel lymph node biopsy help your doctor determine what additional treatment you might need. Doctors typically do a sentinel node biopsy right before a wide local excision. The wide local excision is a second surgery to remove more tissue around the melanoma.
What to expect during this surgical biopsy
The sentinel lymph node biopsy involves a couple of steps. First, the surgeon needs to figure out which lymph nodes drain the primary melanoma site and are most likely to contain cancer cells. For example, if the lesion is on your leg or foot, the nearest lymph nodes would be in your groin. To discover the location of the nodes, the surgeon does lymph node mapping. The surgeon injects a small amount of radioactive tracer material into your skin near where the melanoma was. It takes less than an hour for the tracer to follow the same path as a melanoma cell would to the nearest lymph nodes draining that body area. The surgeon uses a special machine that detects radioactivity called a Geiger counter to see where the malignant cells are most likely to go. The doctor also may inject a blue dye, which travels to the node to identify it.
Many medical centers do the mapping on the same day as the surgery, so you need only one injection of radioactive tracer. In that case, the surgeon only injects blue dye and can use the handheld probe to find the radioactivity injected earlier in the day or the prior day.
The lymph node that shows up with radioactivity is called the sentinel lymph node. This lymph node is the first one to receive the drainage from that part of the skin that was injected with the tracer. 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 to remove normal tissue around the melanoma. This can help prevent melanoma from recurring. Then, the pathologist examines the sentinel lymph node to look for melanoma.
If the removed lymph node does not have melanoma cells, it is called negative. You might not need additional tests.
If the removed lymph node does have melanoma cells, it is positive. In that case, 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 biopsy
If your doctor suspects the cancer has spread, you may have a fine needle aspiration biopsy. This is another procedure used to biopsy nearby lymph nodes or internal organs. You may first get a local anesthetic to numb the area. The doctor uses a syringe with a small needle to remove small tissue fragments from the tumor. The doctor may use a computed tomography (CT scan) or ultrasound to help guide the needle into the tumor.
Computed tomography (CT) scan
This test helps your doctor see where the melanoma is located and whether it has spread to other parts of your body. It is helpful for spotting melanoma in the chest, abdomen, and pelvis.
A CT scan is a more sensitive X-ray that produces cross-sectional pictures of your body using an X-ray machine linked to a computer.
To have the test, you lie still on a table as it slowly slides through the center of the CT scanner. Then the scanner directs a continuous beam of X-rays at your body.
A CT scan is painless and noninvasive. 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. Then you may be asked not to eat anything until a second set of pictures is taken within 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 flushing reaction to the injection. Be sure to tell your doctor if you have a strong reaction to contrast material, such as hives or trouble breathing, or if you have had a reaction in the past.
Magnetic resonance imaging (MRI)
This test is helpful in examining your brain and spinal cord. Or it may 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 different types of tissue and diseases. This produces cross-sectional “slices” of the body, including ones that are parallel with the length of the body.
For this test, you lie still on a table as it passes through a tube-like scanner. It directs a continuous beam of radiofrequency waves at the area being examined. A computer uses data from radio waves to create pictures of the inside of your body. You may need more than one set of images. Each one may take two to 15 minutes. This test is painless and noninvasive. It may last an hour or more. Ask for earplugs or headphones for music if they aren’t offered since there is a loud thumping noise during the scan. If you are claustrophobic, you may be given a sedative before having this test.
Positron-emission tomography (PET) scan
PET can scan your entire body, so it can be more helpful than a series of several different X-rays. For this test, you either swallow or get injected with a biochemical substance, such as glucose. This substance carries a mildly radioactive substance. These two substances together are called a radioisotope. The PET scan will show where in the body the glucose is mostly being used to help spot active, quickly dividing cells, 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. A PET scan is painless and noninvasive. Some people are sensitive to the isotope, 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.
No specific blood tests can give direct information about melanoma. But your doctor may recommend 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 whether or not cancer has spread.
An X-ray is used to see whether there are any changes in your lungs that may suggest the melanoma has spread. An X-ray of the chest uses radiation to make a picture of the organs and bones inside your chest. The test can spot enlarged lymph nodes in your chest area. This test requires no advance preparation. It only takes a few minutes, and causes no pain.