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 include:
- Darkly pigmented skin lesion, sometimes with areas of scanty pigmentation
- Irregularly shaped skin lesion
- Growth or change in shape in a previous mole
- Itching, ulceration or bleeding in a previous mole
Staging of 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.
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 aggressive growth.
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