Melanoma

Melanoma accounts for the majority of skin cancer deaths, but fortunately it is the rarest of the common skin cancers.  It is nearly always curable of diagnosed early.
Melanoma does not always develop from a pre-existing most. In fact this occurs only 50% of the time.
You must be on the look out for change in a mole, but also be highly suspicious of any newly appearing spot on your skin, especially if it is dark in colour and seems to stand out from surrounding skin spots.
Melanoma can occur at any age, though is very rare prior to puberty.                                        Melanoma does have a strong genetic tendency, so family history is important.  Indeed some families are extremely prone.  It is not restricted to the maximally sun exposed areas and sometimes it occurs in areas that have never seen the sun.
What should I look out for?
1. Melanoma should be suspected in the following situations:
2. Sudden or recent change in a mole
3. The recent appearance of a new dark spot or “freckle”, especially if it is enlarging and looks different to nearby spots.
4. The recent unexplained appearance of a spot of any colour, especially if it is continuing to grow and if you are over the age of 40.
Melanoma is diagnosed with a  skin biopsy and pathologist's subsequent microscopic examination. Clues to the diagnosis lie in careful history, examination including dermoscopic examination. Dermatoscopes are instruments which utilise magnification and special illumination to allow doctors to see into the top layers of the skin and examine the structures of the lesion in much more detail.
Treatment always involves surgery, but the degree of surgery required varies according to the melanoma in question. In general though, early melanomas do not require radical surgery.
Early melanomas do not usually require any further treatment or investigation. Patients with a more advanced melanoma will frequently require further tests to see if the melanoma has spread beyond the skin and may well require additional surgery, radiotherapy or chemotherapy.
Remember, virtually all melanomas diagnosed early will be cured, and that delay in diagnosis is the major reason why melanomas become more advanced.  For this reason, those who have an increased risk of melanoma, are advised to undergo regular screening. Very advanced melanomas are rarely curable.

Further reading:
Moles
Dysplastic naevi

Skin Screening

Dermoscopy