These lesions are difficult to diagnose and the patient may only have noticed a minimal change in a long standing mole such as in size, shape or colour.
A pre-invasive melanoma is almost always cured by complete local excision.
The terms dysplastic naevus and melanoma-in-situ may be used.
If you are worried about a skin lesion, the best way to be sure is to have a trained health professional such as your family doctor check it for you. They look at lesions just like those on this site every day and become experts at picking up the ones which require the attention of a skin specialist.
A good way of remembering the tell tale signs of melanoma is the ABCDE system