How Is Metastasis Detected?
If your doctor suspects that your melanoma may have spread, there are several tools available to verify the diagnosis. These include a blood test for lactate dehydrogenase (LDH), which increases when melanoma metastasizes, and imaging studies, such as chest x-ray, computed tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET) and ultrasound. The doctor may also need to take a sample of your lymph nodes, using a procedure called "sentinel lymph node mapping." If confirmed, there are many treatments available, including chemotherapy, immunotherapy, radiation therapy and surgery.
Where Melanoma Spreads
Studies have shown that melanoma can spread to almost any area of the body — a wider variety of areas than any other cancer. The likelihood that it will spread to each organ is as follows:
- Lymph Nodes: 70% to 75%
- Other areas of the skin, fat and muscle: 65% to 70%
- Lungs and area between the lungs: 70% to 87%
- Liver and gallbladder: 54% to 77%
- Brain: 36% to 54%
- Bone: 23% to 49%
- Gastrointestinal tract: 26% to 58%
- Heart: 40% to 45%
- Pancreas: 38% to 53%
- Adrenal glands: 36% to 54%
- Kidneys: 35% to 48%
- Spleen: 30%
- Thyroid: 25% to 39%
Metastasis in the brain usually occur late in stage IV disease and carry the worst prognosis, with an average survival of only 4 months.
Can Metastasis be Prevented?
Melanoma can spread "silently," meaning that you may not experience any symptoms of metastasis. Therefore, if you've been treated for early-stage melanoma in the past, it is extremely important to perform regular self-examinations of your skin and lymph nodes, to keep all your appointments for checkups, and practice sun safety. There is nothing else an individual can do to prevent metastasis besides being very diligent. Catching a recurrence early greatly increases your chances of a successful treatment. If the melanoma does spread, it is important to remain positive: remember that while the average prognosis is poor, some people do survive stage IV melanoma.
"Melanoma: How It Returns, Where It Spreads." American Academy of Dermatology. 20 January 2009.
King DM. "Imaging of metastatic melanoma." Cancer Imaging 2006 6:204-8. 20 January 2009.