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Melanoma is a malignant tumor of melanocytes. Melanocytes
predominantly occur in the skin but can be found elsewhere, especially
the eye. The vast majority of melanomas originate from the skin.
Causes of melanoma
Solar radiation, comprising of UvB (280-320nm) and UvA (320-400nm),
is the major causative factor and the risk is related to :
- The degree of solar exposure.
- Natural skin pigmentation.
- The age at which solar exposure occurs:
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.
Other risk factors include the "Dysplastic naevus syndrome" which
is a familial condition of atypical moles carrying a low to moderate
risk of acquiring melanoma.
Pathological types of melanoma
- Superficial spreading (often fairly thin).
- Nodular (often deeper)
- Acral lentiginous (on soles and palms).
- Hutchinsons melanotic freckle (often in older patients).
Symptoms and signs of melanoma
Diagnosis of melanoma requires expert knowledge, as early stages
may look identical to harmless moles. Signs and symtoms of melanoma
- Darkly pigmented skin lesion, sometimes with areas of scanty
- Irregularly shaped skin lesion
- Growth or change in shape in a previous mole
- Itching, ulceration or bleeding in a previous mole
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Staging of melanoma
of malignant melanoma
Treatment of melanoma
Surgical excison - usually curative in thin lesions. Immunotherapy
and to a lesser extent chemotherapy may have a somewhat experimental
role in advanced tumors.
Chemotherapy regimens in melanoma
Prognosis of melanoma
Features that affect prognosis are tumor thickness in mm (Breslow
depth), depth related to skin structures (Clarke), 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