Information about the impacts of congenital melanocytic naevi (CMN), its impacts on your appearance, and what we can do to help.
Congenital melanocytic naevi (CMN) are moles (“melanocytic naevi”) which are present from birth (“congenital”), or which develop in the first two years following birth. They tend to be larger than moles which develop later in life (“acquired melanocytic naevi”). CMN may vary in size, shape and texture.
In some people, CMN may be relatively unobtrusive, while in rare cases they can cover four-fifths of the body. However large or numerous they are, you may be conscious of your CMN and this can take a toll on your mental health.
On this page, we look at the different types of congenital melanocytic naevi, causes of the condition, the impact it can have on your wellbeing – and what we can do to help.
Note: You may wish to view this page alongside our page on moles, which also covers acquired melanocytic naevi. CMN and moles are a form of hyperpigmentation – we have a page on this broader set of conditions which you can have a look at.
I now know… that all the love and abundance in my life would not be here without my birthmark. It has been part of me from day one and its existence has shaped my life and made me the person I am today.
Congenital melanocytic naevi are often classified according to their size although, nowadays, categorisation by size isn’t as common as it used to be. We include common size classifications below as they may be useful when researching your naevi. However, please be aware that your doctor or dermatologist may use different sizes or none at all.
A large congenital melanocytic naevus on a darker-skinned newborn (Image by Mohammad2018, CC BY-SA 4.0 via Wikimedia Commons)
These classifications apply to the size of CMN in an adult. In CMN, naevi usually start off smaller in children and grow in proportion to the child. Occasionally, naevi shrink or become less obvious over time. In very rare cases, they disappear. Conversely, they can become darker, raised, bumpy or hairier, with changes most commonly happening around puberty.
CMN vary in appearance. They may be:
CMN are usually free of sensation and behave the same way as the surrounding skin. Symptoms sometimes occur, however, including:
In rare cases, a syndrome called neurocutaneous melanosis can occur. It is caused by melanocytes in the central nervous system (brain and spinal cord) and occurs almost exclusively in cases of giant CMN with satellite lesions. This condition may cause increased pressure in the skull (intracranial pressure). It can lead to symptoms such as headaches, vomiting and mood changes, as well as more severe symptoms in some cases.
A medium congenital melanocytic naevus on a light-skinned adult (Image by CDC, public via Wikimedia Commons)
Melanoma (cancer) is rare in congenital melanocytic naevi. The risk is heightened with large or giant naevi – although even in this case, lifetime risk is judged to be only around 5-10%. Even this may be an overestimate, with one large study putting the rate at 2.73%.
Other risk factors include:
The risk of cancer tends to be highest in childhood, with 70% of cancers in giant CMN occurring before the age of 10.
Congenital melanocytic naevi, like all moles, are caused by the occurrence of a large number of benign melanocytes. “Benign” means they are not dangerous, while “melanocytic” refers to melanocytes – the cells that make the pigment “melanin”, which gives skin its colour. It is because melanocytes are present in large numbers that moles may appear darker than the surrounding skin, especially in people with lighter skin.
The underlying cause of CMN is a genetic change which usually occurs between the fifth and 24th weeks of pregnancy. If the change occurs earlier in pregnancy, the naevi are often larger in size.
Yes, as discussed above, congenital melanocytic naevi are caused by a genetic change which occurs during pregnancy. However, this genetic change happens spontaneously, as CMN are not inherited from either parent.
In this form of congenital melanocytic naevi, the name refers to the position on the body. Garment naevi usually occur where particular items of clothing might end – for example, just above the top of a pair of shorts or on the shoulder above the sleeve of a T shirt. However, there can be significant variation – for example, a garment naevus could cover the entire arm.
In halo naevi, the surrounding skin becomes lighter or white and, in some cases, the central lesion may become lighter or smaller, or may even disappear. This is caused by the destruction of melanocytes by the immune system.
Kissing naevi occurs when the genetic change that causes CMN takes place very early on in pregnancy, before the upper and lower eyelids of the foetus have separated. In kissing naevi, the naevus spreads across eyelids.
In organoid naevi, hairs grow on the mole(s).
Satellite lesions tend to be found on the edge of a central CMN or elsewhere on the body. More than 70% of patients with a large CMN have these.
This appears as a dark spot on a tan background. The number of speckled lentiginous naevi may go up or down.
Tardive naevi appear after birth due to slower production of melanin. “Tardive” comes from the Latin “tardus” meaning late or slow (as in “tardy”).
Katie worried that because her visible difference was not as prominent as some people’s, she didn’t deserve support. But after years of comments and stares, Katie was desperate for help. Becoming a Changing Faces campaigner changed her life.
Read Katie’s storyDiagnosis is usually carried out by visual examination. If there is uncertainty surrounding the diagnosis, a dermoscopy may be used. A dermoscopy is an examination of the skin under magnification.
Surgery and treatment is usually avoided in congenital melanocytic naevi, unless there is a particular reason for medical intervention, such as the development or heightened risk of cancer.
In CMN, surgery may take place:
Having congenital melanocytic naevi may make you feel self-conscious about your appearance, whatever the size or prominence of your CMN. However, you may feel more self-conscious about naevi which are highly visible – such as on your face or exposed parts of your body. You may feel you have to conceal or cover your naevi.
You may feel that people are looking at you and feel uncomfortable if they ask questions. This can be upsetting, and some people find that it affects their mental health and self-confidence. It may be that this is only occasionally a problem for you, or it may interfere with your day-to-day life.
Here at Changing Faces, we offer a number of support services if you are struggling with the impact of congenital melanocytic naevi on your appearance.
As with any visible difference, living with CMN can affect your social, emotional and psychological wellbeing. We offer counselling and wellbeing support to help with these impacts. Our trained practitioners will listen to you and provide guidance to help you get through the challenges you are facing. Have a look at our page to see whether counselling and wellbeing support might be helpful for you.
We also have a selection of online self-help guides covering topics from self-esteem and mental health to dealing with people’s reactions, as well as working life and dating with a visible difference like CMN.
Our section for young people also covers topics including school, making friends, social media and body image. Alongside this, we have guidance for parents and carers.
You don’t have to hide your CMN to fit in with what society expects. However, some people choose skin camouflage to reduce the appearance of their CMN. The effect will vary depending on whether your marks are raised and/or textured, but our Skin Camouflage Service team would be happy to speak to you about whether skin camouflage may be helpful to you. Start by reading more about our Skin Camouflage Service here on our website.
We provide other services for people with CMN and other visible differences:
You can find out more by contacting our Support and Information Line. As well as connecting you with our services, our team offer support calls so you can talk about the impact of CMN on your life.
Guidance, support and advice is also available from other organisations. Please follow the links to their websites to learn more.
Caring Matters Now is the UK charity supporting those affected by CMN. As well as funding research and raising awareness, Caring Matters Now provides support to people with CMN and their families, including help with specialist referral, events, peer support and resources.
A national, highly specialist psychological service based at North Bristol NHS Trust, supporting adults (16+) with appearance-related distress. They can provide face-to-face and remote support via NHS Attend AnyWhere. Please speak to your GP or healthcare professional to discuss a referral.
Please have a look at the NHS condition page for official guidance on moles, information on when to see a GP, and advice about treatments available on the NHS. You will also find out what treatments are available on the NHS and how to seek help.