Malignant melanoma
Melanoma is a malignant tumour of melanocytes . Melanocytes predominantly occur in the skin but can be found elsewhere, especially the eye. The vast majority of melanomas originate in the skin.
What causes Melanoma?
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
- the intensity and duration of solar exposure
- the age at which solar exposure occurs
- 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 "Superficial spreading malignant melanoma (SSMM)
- Nodular melanoma
- Acral lentiginous melanoma
- Lentigo maligna melanoma
- Amelanotic melanoma
Prognostic factors
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.
Treatment
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. In metastatic melanoma chemotherapy, immunotherapy, gene therapy, as well as local perfusion are experimental forms of therapy used by different centers. They can occasionally show dramatic success, but the overall success in metastatic melanoma is quite limited.
