Melanoma, accounting for less than 5% of skin cancers, is one of the most dangerous of all cancers and is the most rapidly increasing form of cancer in the United States. Melanoma arises from pigment cells in the skin and usually takes the form of a very dark, irregularly-colored spot or nodule. The risk of melanoma is increased with occasional, intense exposure, such as blistering sunburns, especially in childhood, rather than long-term sun exposure.
Unlike other cancers, melanoma may remain inactive for years, may even regress temporarily, and then suddenly metastasize to lymph nodes or vital organs. The tendency of melanoma to metastasize is fairly predictable and is related to the thickness rather than the size of the tumor.
Melanoma is more common in younger individuals. In the United States, the risk of melanoma is about 15 cases for every 100,000 people, and at the time of writing (2002) there will be 40,000 new cases with about 8,000 deaths expected in the next year. Incidence is doubling every 10 years, and this is believed to be mainly due to the depletion of the ozone layer.
Melanoma may occur by itself, or arise from a pre-melanoma mole or skin growth.
Australia has the world's highest incidence of melanoma, because of its location near the equator and population composed largely of people of Celtic extraction. The fact that melanoma occurs mainly on sites not overly sun-exposed indicates that other factors are involved.
In brief, the risk factors are:
Common locations for melanoma include the back and scalp in men and legs in women, areas not usually exposed extensively to the sun.
Major signs of malignant melanoma:
Minor signs of malignant melanoma:
The systemic evaluation for melanoma metastases involves:
Five year survival related to tumor depth:
Survival rates are better in women.
Dark lines beneath the nail should be investigated as soon as possible.
A longitudinal brown-black streak (which may take up the whole nail and may "spill over" into the proximal nail fold) is a sign of melanoma, and possibly Hutchinson's.
Melanomas may initially look like moles, but distinguish themselves from normal moles by changing in size (enlarging), shape and color. In other words, melanomas become larger, more irregularly shaped and usually darker and more uneven in color.
Individuals with a parent or sibling with melanoma have a 10 times greater chance of developing melanoma themselves.
A person who has more than 5 atypical or "dysplastic" moles has a higher risk of developing melanoma and should check their skin thoroughly several times per year to look for changes.
See the link between Cancer (General) and Hydrazine Sulfate.
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