How is melanoma diagnosed?
Normally, your GP will be the first to examine you. If they think you have melanoma, you will be referred to a specialist (dermatologist).
The specialist will examine your moles and will ask you about any changes you may have noticed and the time the moles have been there. They will also examine the rest of your body to see if there are other unusual moles.
Some specialists can examine your moles with a small instrument called a dermoscope. This produces a bigger and clearer image of the mole. It is important to know whether a mole has changed over time.
If melanoma is suspected, you may be advised to have the mole removed to find out what it is; this is called an excision biopsy.
You will be given a local anesthetic for the area around the mole to put the area to sleep and prevent discomfort. The entire mole and at least a 2-mm minimum diameter of healthy skin will be removed. Afterward, the wound is closed up with sutures; these may be taken out in 5-14 days or may dissolve by themselves. The mole will be examined under a microscope by a pathologist to see if there are any cancer cells.
- Sentinel node biopsy (SNB)
This may be done whether or not there is swelling of the lymph nodes. Sentinel nodes are the first to drain lymph fluid from the melanoma and are the first to be involved by the cancer.
A sentinel node can offer information on the stage of the cancer.
A small amount of mildly radioactive liquid is injected to the area around the melanoma to observe which lymph nodes the liquid travels to; these are the sentinel lymph nodes.
They are removed and sent to the laboratory for examination under a microscope to see if they contain cancer cells. If the sentinel lymph nodes do not contain cancer cells, it is unlikely the other lymph nodes have been affected, meaning it will not be necessary to have them surgically removed. If they contain cancer cells surgery will be required to remove all the lymph nodes around the melanoma.
- Ultrasound and fine-needle aspiration (FNA)
If some of the lymph nodes are swollen, ultrasound-guided fine-needle aspiration may be recommended to check them.
Just because the lymph nodes have become inflamed does not necessarily mean the melanoma has spread; indeed, the cause may be an infection.
Ultrasound uses sound waves to create an image of a particular area in the body. The procedure is painless and only takes a few minutes. A gel is applied over the area where the lymph nodes to be examined are located, and a small device containing a microphone that emits sound waves is passed over the area. A computer converts the sound waves into an image. If abnormalities are observed in the lymph nodes, FNA is performed.
- Fine-needle aspiration
FNA is a simple and quick procedure. A thin needle is inserted into the lymph node, extracting cells through a syringe. These cells are then examined under a microscope to check for cancer.
- CT (computed tomography)
A CT takes a series of x-rays, creating a 3-D image of the lower part of the body.
It can be used to identify the exact location of the tumor or to check whether the cancer has spread. These studies take from 10 to 30 minutes and are painless.
A small amount of radiation is used, though it is very unlikely to cause you any harm. You will be asked to refrain from eating and drinking for at least four hours before the test.
You may be given a drink or an injection with a dye, which makes it possible to see certain areas more clearly. This may make you feel hot for a few minutes. It is important that you inform your health professionals if you are allergic to iodine or have asthma, as you may have a reaction to the injection.
CT scans can also be used as a guide during biopsies.
- MRI (magnetic resonance imaging)
This test uses magnetism to build a detailed image of one of the areas of your body. The scanner is a powerful magnet, which is why you will be asked to fill out and sign a checklist and provide your consent. As part of this consent form, you will be asked if you have any implants such as a pacemaker or surgical clips. You should also tell your doctor if you have ever worked with metals or in the metal industry.
Before the scan, you will be asked to remove all metal belongings, including jewelery. Sometimes, a contrast dye is given by injection in a vein of the arm to help the images come through more clearly.
You will have to remain very still during the test, which lasts about 30 minutes. The process is painless but can be somewhat uncomfortable, and some people experience a bit of claustrophobia. It is also quite loud, though you will be given earplugs or headphones.
- PET (positron emission tomography)
A PET scan uses slightly radioactive sugar substance to measure cell activity in the body. Before the scan, a small quantity of radioactive liquid is injected into a vein, normally in the arm. Areas of cancer are normally more active than the surrounding tissue, causing them to absorb more sugar; this shows up during the scan and points out the areas that contain cancer.