Dermatoscope image of a mole on the lower leg of a 67 year old Hispanic male patient. This type of mole is known as a junctional melanocytic naevus. It is caused by the proliferation in melanocytes, the skin cells that produce the pigment melanin. Most moles are harmless, but they can turn cancerous. This is usually indicated by a change in colour or size, or by them becoming itchy.