It's normal to have moles or freckles on your skin, as in most cases, they're harmless. However, if a mole begins to look unusual or change in appearance, it could be skin cancer. It's vital to keep an eye on your moles and freckles to better understand whether or not they may be cancerous. Here's what to look out for: Melanomas often have an uneven shape (asymmetrical). The two halves might be a different shape or size, whereas the two halves of a normal mole are often symmetrical. Melanomas often have an irregular, blurry, or jagged border, whereas normal moles usually have a smoother, more regular border. Cancerous moles will be an uneven color, and contain more than one shade. This is typically different shades of black, brown, and pink. Regular moles, in comparison, are often an even color. Keep an eye on the width of the mole; most melanomas are more than 6 mm wide; however, they can be smaller if diagnosed early. Normal moles are around the size of the end of a pencil. Melanomas can easily change in size, shape, or color, and they can also be itchy or start bleeding or even develop a crust.