are round in shape and roughly symmetrical. Melanomas
on the other hand, often look different from your typical moles. They are often (but not always) asymmetrical. A good way to test this is to draw an imaginary line through the center of the mole. If it creates roughly equal parts, with similar shapes, the lesion is symmetrical.
First, look at his image of a mole.
This mole is roughly symmetrical. If you draw an imaginary line though the center of the lesion, you should see a very similar shape between the left and right side of the line.
Note that the lesion is not symmetrical. Imagine drawing a line through the center of the lesion. You will not get equal looking halves from the mole image (on the left).
Next: Border Irregularity