http://metro.co.uk/2017/05/12/handy-animated-guide-shows-you-the-abcde-of-spotting-skin-cancer-6632327/
Quoting:
"Warning signs of skin cancer:
Asymmetry: An irregularly shaped mole
Borders: Ragged edges instead of a defined line could be a sign of skin cancer
Colour change: If a mole changes colour or is different colours in different parts, talk to a GP
Diameter: Any changes in size should be checked out
Elevation: Raised moles that become more or less raised may need to be checked"
