There are differing names for various types of moles, also known as nevus, these include: acquired moles, also known as a common mole, congenital moles, often referred to as birthmarks, and atypical moles, also termed as dysplastic nevi.
What is an Acquired Nevus or Common Mole?
Acquired or Common moles are those that we usually see starting to appear in childhood and adolescence. Appearing anywhere on the body, they are small in size – less than 5mm – have a smooth sometimes domed surface, and are oval or round in shape, with an even colour. Most adults will have between 10 – 40 common moles on their skin. These may darken or lighten over time. Common moles seldom become cancerous.
What is a Congenital Mole?
A congenital mole is one that is present at birth or that appears up to a year afterwards and can appear anywhere on the body. These can vary in size, from small melanocytic nevus less than 2cm in diameter, to giant melanocytic nevus, covering almost the entire body – though this is rare and has historically only affected 0.002% of births – there is an increased chance of melanoma in cases where the congenital birthmark is larger than 20cm.
What is an Atypical Mole or Dysplastic Nevus?
An atypical mole or dysplastic nevus is bigger than a common mole – larger than 5mm – has an irregular shape and colouring, may be smooth or have a slightly scaly surface. This type of mole usually appears on areas of the body that have endured greater sun exposure including, breasts, areas below the waist, and the scalp. There is an increased risk of melanoma for those who have atypical or dysplastic nevus.