Moles (birthmarks), also called naevi, are benign pigmented cells in the skin. Almost everyone has moles; an average person has about twenty of them. Exposure to the sun in particular is an important factor for their development. Moles are benign as long as they don’t change shape or colour. Some moles, however, can develop into melanoma: a malignant mole. To recognize a malignant mole/melanoma, you can use the so-called ABCD rule:
If a mole is asymmetrical, has a uneven border / irregular boundaries, has two or more colours or has a diameter larger than 6 mm, it is highly recommended to have your mole checked by a doctor. Also when a mole hurts, starts bleeding or itches, it’s very important that you have it checked.