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Epidemiologic studies suggest that exposure to ultraviolet radiation is one of the major contributors to the development of melanoma. Other candidates are mutations in or total loss of tumor suppressor genes.
Important factors in determining risk include the intensity and duration of solar exposure, the age at which solar exposure occurs, and the degree of skin pigmentation (see skin types ).
Exposure during childhood is a more important risk factor than exposure in adulthood. (This is seen in migration studies in Australia where people tend to retain the risk profile of their country of birth if they migrate to Australia as an adult). Fair and red-headed people are at greater risk.
Some other risk factors include the "dysplastic naevus syndrome ", a previous history of melanoma, and a history of melanoma in the immediate family.
Diagnosis of melanoma requires expert knowledge, as early stages may look identical to harmless moles or not have any color at all. Beyond this expert knowledge a biopsy is often required to assist in making the diagnosis, confirming the diagnosis and in defining the severity of the melanoma.
A popular method for remembering the signs and symptoms of melanoma is the mnemonic ABCD:
- Asymmetrical skin lesion
- Border of the lesion is irregular
- Color: melanomas are often black but can be multicolored; any change in color should prompt a doctor's visit.
- Diameter: any mole that increases in diameter or any large mole should be seen by a dermatologist.
Sometimes the skin lesion may bleed, itch, or ulcerate. A slow-healing lesion should be watched closely, as that may be a sign of melanoma.
Types of melanoma
- Superficial spreading malignant melanoma (SSMM)
- Nodular melanoma
- Acral lentiginous melanoma
- Lentigo maligna melanoma
- Amelanotic melanoma
Features that affect prognosis are tumor thickness in millimeters (Breslow's depth), depth related to skin structures (Clark's levels ), type of melanoma, presence of ulceration, presence of satellite lesions, and presence of regional or distant metastasis.
With regard to tumor thickness at the time of diagnosis: thin melanomas (<0.75mm) have a good prognosis, i.e. they can usually be cured by surgical excision alone; tumors of more than 4 mm thickness at the time of diagnosis are very often metastatic and can show very aggressive growth.
Complete surgical excision with adequate margins and assessment for the presence of detectable metastatic disease along with short and long term follow up is standard. A "sentinel lymph node" biopsy is often included for melanomas of the limbs.
In metastatic melanoma chemotherapy (15-20% respond to dacarbazine , also termed DTIC), immunotherapy (with interleukin-2(IL-2) or interferon) as well as local perfusion are used by different centers. They can occasionally show dramatic success, but the overall success in metastatic melanoma is quite limited. IL-2 (Proleukin®)is the first new therapy approved for the treatment of metastatic melanoma in 20 years. Studies have demonstrated that IL-2 offers the possibility of a complete and long-lasting remission in this disease.
Radiation therapy is often used after surgical resection for patients with locally or regionally advanced melanoma or for patients with unresectable distant metastases. In research setting other therapies, such as gene therapy, may be tested.
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