Melanoma is an important representative of skin cancers. It is a very dangerous tumor with unpredictable behavior. It can be prevented, but the treatment of its late forms is not very effective. Melanoma arises from pigment cells (melanocytes) that are mainly located in the human skin. About two thirds of melanoma cases occur in a normal skin and the rest develops from preexisting birthmarks.
The greatest risk factor is excessive exposure to UV radiation without using the protective creams. Repeated acute sunburn is especially harmful. Both the sunlight and tanning are dangerous. In addition, the disease may have some relationship to genetics. The black race is more resistant to the sunlight and the risk of melanoma is much lower. The Caucasians are much more endangered, especially those with blond or red hair.
Melanoma has an appearance of more or less bizarre mole (birthmark). See more details below (Prevention and diagnostics). The problem is that it may occur practically anywhere on the skin including areas, where there is problem to find the lesion in time (the back, under the nails, in hair-covered area, around the anus, etc.). Some insidious forms of melanoma do not grow from the skin at all but they develop from pigment cells within other tissues, for example in the eye and in brain meninges. The tumor tends to form metastases that may occur virtually in any organ including liver, lungs, intestines, heart and brain. The advanced symptoms usually include weight loss, fatigue, night sweats and malfunction of the affected organs.
Prevention and diagnostics
Prevention is essential as first stage of melanoma is easily curable. Each person should regularly check the skin and any visible pigmented spots. This includes the limbs and the back as the melanoma can occur practically anywhere on the skin. Every pigment spot is suspicious when:
- it is multicolored (parts brown, parts darker or lighter)
- it has an asymmetrical shape with irregular edges
- it is not sharply demarcated from the surrounding
- it is bleeding
- it is larger (above 0.5cm) and grows
Any skin lesion with such attributes should be inspected by a doctor, in ideal case by a dermatologist. Most melanomas initially grow rather superficially and at this moment, they are completely harmless. If melanoma is detected at this stage, the chance of a curative treatment is about 100%. Later, melanoma penetrates deeper and the risk of metastases sharply increases. The risk is expressed by the Breslow score, which take account the tumor’s depth:
- The depth of penetration is below 1 mm (Breslow < 1 mm). The 5-year survival is over 95%.
- The depth of penetration is above 1 mm (Breslow > 1 mm). The 5-year survival is les than 70%. This value further decreases when the local lymph nodes are affected in time of the diagnosis. Presence of distant metastases is related to minimal chance of survival.
The diagnosis is usually done by a dermatologist. The lesion can be inspected by the naked eye and by a special device known as dermatoscope, which magnifies the lesion and provides a source of high-quality light. When there is a suspicion, the lesion is surgically removed and histologically examined. The surgery may include removal of the so-called sentinel lymph node, which is the lymph node draining tissues neighboring the tumor.
The diagnostic surgery is in ideal case also the therapeutic method. The surgical intervention should consist of excision of a certain rim of healthy tissue to prevent local recurrence.
After the surgery, the patient is usually regularly checked including repeated chest X-ray and abdominal ultrasound to exclude occurrence of distal metastases. It is also possible to evaluate the tumor markers, which are natural substances that may be elevated in case of a tumor presence. They are not suitable for primary detection of a tumor presence, but they are suitable for the detection of increase or decrease of the tumor mass over time. The most used tumor marker for melanoma is the S-100 protein.
The tumor responds badly to chemotherapy, but new therapeutic methods should sharply improve the therapeutic outcome in the near future.