Atypical naevi

What are atypical naevi?

Atypical naevi are moles (melanocytic naevi) that have unusual features such as an indistinct edge and/or larger size. They may resemble a cancerous mole (malignant melanoma), but are actually benign.

They are also sometimes called dysplastic naevi, but this is term is best used by pathologists for a specific microscopic appearance. Other names for atypical naevi include active junctional naevi, B-K moles and Clark's naevi.

There are basically two types of atypical naevi, sporadically occurring atypical naevi and familial (inherited) atypical naevi. The inherited form is usually part of a syndrome called familial atypical mole and melanoma (FAMM). FAMM syndrome was previously known as Dysplastic naevus syndrome.

People with FAMM syndrome must have the following:

• One or more first-degree or second-degree relative with malignant melanoma
• Presence of a large number of naevi (often more than 50) some of which are atypical naevi
• Naevi that show certain histological features.

What do atypical naevi look like?

Atypical naevi can be considered funny looking moles.

• They may be larger than average (5-15mm)
• They may be an unusual shape or have a notched or blurred border.
• The colour is variable and may be pink, brown or black.
• The surface may be bumpy or smooth.
• They have characteristic dermoscopic features.
• They may have atypical or dysplastic features on biopsy.

Atypical naevi

More images of atypical naevi ...

Atypical naevi may appear anywhere on the body but are most commonly found on the back, chest, buttocks and scalp. They are more common in areas that have been exposed to the sun. The number of atypical naevi present is variable. People with FAMM syndrome may have several hundred lesions. Typically, those with sporadic atypical naevi have one to ten lesions.

Who is at risk of atypical naevi?

Fair-skinned individuals with light coloured hair and freckles (phototype 1-2) are most at risk of getting atypical naevi, especially if they have been frequently exposed to the sun or have a family history of atypical naevi. Atypical naevi may develop at any time throughout life but most of them develop during childhood, usually within the first 15 years of life.

What does it mean if I have atypical naevi?

People with one to four atypical naevi have a slightly higher risk than the general population of developing malignant melanoma, whilst people with FAMM syndrome are significantly more at risk of developing melanoma.

Atypical naevi are harmless (benign) and do not need to be removed. However, it is not always easy even for an experienced dermatologist to tell whether a lesion is an atypical naevus or a melanoma, so if in doubt, it should be removed by excision biopsy. A pathologist will usually make the correct diagnosis.

People diagnosed with atypical naevi should be taught how to self-examine their skin for new moles or for changes to existing moles that may indicate melanoma development. If you have numerous moles you should visit your family doctor or dermatologist regularly for a thorough skin check.

It is often helpful to keep photographic records of the naevi; digital archiving is convenient. The close-up should be repeated from time to time. Dermoscopic views enable your dermatologist to detect change early. You may like to attend a mole mapping clinic.

Careful sun protection is recommended: avoid excessive sun exposure and use a SPF15+ sunscreen.

A skin biopsy may be necessary if moles change and melanoma is suspected.