Atypical Moles or Dysplastic Naevi

What are atypical moles?

Atypical moles, also called dysplastic naevi, are moles that look different from ordinary moles. They are usually larger, with an irregular shape, blurred edges and more than one colour. The word dysplastic means that the cells in the mole look unusual under the microscope, but it does not mean the mole is cancerous. Most atypical moles stay harmless throughout life.

Atypical mole syndrome describes people who have a large number of moles, more than 50, of which three or more are atypical.

Who gets them?

Atypical moles are fairly common. About 1 in 15 white people has at least one. Atypical mole syndrome affects around 2 in 100 people. Both are seen more in people with fair skin, blue eyes and red hair, especially those of Celtic ancestry, and are uncommon in other ethnic groups.

What causes them?

Atypical moles develop through a combination of inherited factors and exposure to ultraviolet (UV) light. Sunburn in childhood increases the number of moles, including atypical ones.

Are they hereditary or contagious?

Most single atypical moles are not inherited. However, atypical mole syndrome can run in families, and inherited features such as fair skin also increase the likelihood. When atypical mole syndrome occurs in a family with a history of melanoma, it is called familial atypical mole syndrome. Atypical moles are not contagious.

What do they look and feel like?

Atypical moles are usually 5 to 10 mm across or larger, with irregular, indistinct borders. They are frequently oval in shape, and may be partly flat and partly raised. They can contain several colours, such as tan, brown, pink and dark brown or black. The trunk and scalp are the usual sites, but they may develop anywhere, even on skin that rarely sees the sun.

Atypical moles and melanoma

Most atypical moles never become cancerous. However, having many atypical moles is a marker of higher melanoma risk across the whole skin, not just in the atypical moles themselves. People with atypical mole syndrome have a 7 to 10 times higher risk of melanoma than the general population. This risk is greater again with atypical moles on the scalp, feet or buttocks, or with melanoma in the family.

How are they diagnosed?

Atypical moles are assessed by a dermatologist with a dermatoscope, looking at their size, shape and colour pattern. Atypical mole syndrome is usually recognised from the number and appearance of moles. Baseline photographs of the whole skin (mole mapping) and of individual moles are very useful for monitoring change over time. If a mole looks concerning, it may be removed and examined under the microscope, which is the only way to confirm the diagnosis.

What are the treatment options?

Dr Mounsey will examine your moles with a dermatoscope and assess your overall risk of melanoma. Most atypical moles do not need removing. Any mole that looks particularly unusual or is changing can be removed by excision and examined under the microscope. For people with many atypical moles, mole mapping with the Canfield IntelliStudio allows changes to be detected early by comparing photographs over time. He will also advise on self-examination and sun protection, and on checks for close family members where appropriate.

What are the treatment options?

Dr Mounsey will examine the lesion with a dermatoscope and may take a biopsy to confirm the diagnosis and subtype. Most BCCs are treated with surgical excision, which he carries out himself and which gives a high chance of complete removal. Other options include curettage and cautery for small, low-risk BCCs, cryotherapy, creams such as imiquimod or 5-fluorouracil for superficial BCCs.. BCCs on the face or with a higher risk of coming back may be best treated with Mohs micrographic surgery, for which he will refer you to a Mohs surgeon colleague. Radiotherapy is an option for some people.

What is the outlook?

Atypical moles and atypical mole syndrome cannot be cured, but they can be monitored. Regular skin checks by a dermatologist, monthly self-examination, prompt assessment of any changing mole, and careful sun protection all help melanoma to be detected early, when the outlook is excellent.

More information

British Association of Dermatologists patient leaflet on dysplastic (atypical) naevus: https://www.bad.org.uk/pils/dysplastic-atypical-naevus

British Association of Dermatologists patient leaflet on atypical mole syndrome: https://www.bad.org.uk/pils/atypical-mole-syndrome

This page gives general information only and is not a substitute for a consultation. Everyone's skin is different, and what is right for you will depend on your own circumstances. If you are worried about a skin problem, please book an appointment with Dr Mounsey or speak to your GP. If you have a mole or skin lesion that is changing, bleeding or growing quickly, please seek medical advice promptly.