follow @PCDSUKCreated: 19th February 2012 | Last Updated: 24th February 2018
Acknowledgements: to Dr Veronica Kinsler (Consultant Paediatric Dermatologist, Paediatric Dermatology Dept, Great Ormond St Hospital for Children NHS Trust, London) for helping develop this chapter and for providing images 7-10.
Introduction
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Approximately 1% of newborns have congenital melanocytic naevi (CMN). |
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Clinical findings
Lesions tend to be larger in size than acquired naevi and are dark brown or black in colour with deeper extension of melanocytes into the dermis and surrounding appendages.
The size of a single CMN can vary from a few millimetres to many centimetres across, for example affecting most of the trunk and thighs. CMN can be classified based on projected adult size, which is a difficult and largely unhelpful tool in clinical practice. In general, the larger the main CMN the more likely it is to be associated with multiple smaller CMN, sometimes called satellite lesions. Currently the most useful clinical classification is into single CMN (defined as one CMN at birth, of any size or site) and multiple CMN (defined as two or more at birth, of any size or site).
CMN can be hairy at birth or may become hairy over time. Patients can continue to develop new small CMN over time, and this is highly variable between individuals.
Where CMN are associated with non-cutaneous findings this is then termed the CMN syndrome. The older term Neurocutaneous melanosis (the association of CMN on the skin and a subset of congenital neurological disease) is no longer favoured as many other associations are now recognised.
Images
Please click on images to enlarge or download. The PCDS would like to thank Dermatoweb, DermQuest (Galderma), and others who have contributed images. All named individuals and organisations maintain copyright for the relevant images. This website is non-profit and holds the images for educational purposes only. Any image downloaded must only be used for teaching purposes and not for commercial use. Notice and credit must be given to the PCDS or other named contributor. Please follow this link if you have any high-quality images that you can contribute to the website.
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Figure: 1 Congenital melanocytic naevus of the shoulder |
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Figure: 2 Congenital melanocytic naevus of the thigh |
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Figure: 3 Congenital melanocytic naevus of the abdomen |
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Figure: 4 Congenital melanocytic naevus |
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Figure: 5
Dermoscopic appearance of figure 4 |
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Figure: 6 Giant congenital melanocytic naevus Satellite lesions present on buttocks Copied with kind permission from Dermatoweb |
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Figure: 7 Giant congenital melanocytic naevus |
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Figure: 8 Same patient as figure 7 Satellite lesions on lower legs |
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Figure: 9 Same patient as figure 7 Satellite lesions on arms |
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Figure: 10 Close-up of figure 7 |
Management
Complications
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Congenital neurological disease
- This has not so far been described with a solitary CMN at birth, of any size or site
- The main complication of multiple CMN are congenital abnormalities in the central nervous system (CNS)
- Patients with multiple CMN at birth, of any size or site, should have a single screening MRI of the CNS (brain and whole spine with contrast), ideally within 0-6 months of life
- If the MRI scan is normal (80% of cases with two or more CMN at birth) no further routine scans are required, and the patient’s neurological outlook is excellent
- If the MRI scan shows congenital neurological disease this can be divided into a) intraparenchymal melanosis only and b) all other findings (generally complex malformations with or without leptomeningeal disease), and guidelines on further management should be followed
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Characteristic facial features
- Patients with CMN may have typical facial features
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Mild hormonal disturbances
- Patients can present with premature thelarche, or early apparent adrenarche with pubic hair particularly where the CMN involves the pubic area
- Characteristic changes in LH and FSH are usually found in these cases
- True precocious puberty is rare
- Undescended testes can be a feature, particularly in association with “bathing-trunk” distribution CMN
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Melanoma arising in the skin or in the CNS
- The risk of melanoma in patients with a single CMN is very low, likely to be comparable to the risk in an acquired melanocytic naevus. They do not therefore need to be resected prophylactically or routinely monitored in childhood at least
- In patients with multiple CMN the risk of melanoma is most strongly predicted by the results of the screening MRI of the CNS. If normal the risk of all-site melanoma in childhood is of the order of 1-2%, independent of the size or number of the multiple CMN. If abnormal the risk is approximately 12%, although this is mainly for those with complex congenital neurological disease on MRI
- Cutaneous melanoma presents with lumps, often with existing nodal metastasis
- Primary CNS melanoma presents with focal signs or symptoms of raised intracranial pressure
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New treatments based on genetic findings have been trialled recently with symptomatic improvement, but the outcome of melanoma in CMN patients in childhood is still extremely bleak
Spontaneous lightening of CMN
- CMN have been discovered to lighten in line with the patient’s own background skin tone. Hence lighter skinned individuals get more lightening than darker. This happens over a period of years, and the colour of the CMN at birth must not be considered to be an appropriate guide to the final colour (in the same way as hair colour at birth is unrelated to final colour)
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Very importantly superficial removal techniques including laser, dermabrasion and curettage do not alter the final colour of the CMN - any colour change is temporary, and the CMN will gradually resume the colour which is related to the skin tone of the individual. In addition, these techniques can be painful and carry significant risk of scarring. They are therefore not recommended for the treatment of CMN
The role of surgery in the management of CMN
- There is no evidence that surgical removal of CMN alters melanoma risk. This is likely to be because those lesions which can technically be removed completely are at very low risk in any case, whereas those at highest risk are not feasible to remove (and melanoma in childhood favours the CNS)
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Surgical removal for cosmetic reasons does have a place in the management of CMN, particularly for facial lesions, and can involve either serial excision, split-thickness grafting, or balloon expansion (depending on the institution involved in care)
Psychological support of individuals with CMN and their families
- Given the current absence of good treatments, psychological support is frequently extremely helpful, either for parents soon after birth, or for the child, most commonly in early adolescence (or when the individual needs it). Teenage years are unsurprisingly the most difficult. Early referral to appropriately trained clinical psychologists is recommended, with Patient Support Groups also vital for many people
Other resources
- Patient support group for CMN - Caring Matters Now
- There is a weekly dedicated clinic for CMN at Great Ormond Street Hospital