Naevi - Congenital melanocytic naevi |
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Latest update 16/06/09
Acknowledgment
To Dr Veronica Kinsler (Clinical Fellow, Paediatric Dermatology Dept, Great Ormond St Hospital for Children NHS Trust, Great Ormond St, London) for helping develop this article and for providing images 5-8
Key diagnostic features
- Approximately 1% of newborns have congenital melanocytic naevi (CMN) and they are usually present at birth
- 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 can vary from small to very large
- Lesions projected to be > 20cm diameter in adulthood are termed giant congenital naevi
- Congenital naevi often become protuberant and hairy
Complications
I) Neurocutaneous melanosis
The main complications of CMN result from the presence of melanin in the CNS (neurocutaneous melanosis). Although some patients remain asymptomatic, complications include developmental delay, fits and melanoma. The likelihood of having neurocutaneous melanosis correlates most strongly with the size of the CMN, and with the presence of satellite lesions - the finding of other melanocytic lesions in the skin, some of which may be distant to the main CMN. The site of CMN does not appear to be relevant. Current recommendations are that patients should have an urgent MRI if they have any clincial features of neurological complications. Whether or not asymptomatic patients with satellite lesions should be scanned early in life (the first 6 months) is debatable
II) Melanoma risk
- Photographs should be kept of lesions and patients asked to report any changes
Management of CMN
Current recommendations from Great Ormond Street Hospital are that most CMN should not have routine surgical treatment. This decision requires substantial support of the family and patient and good explanation of the reasons for this, which are as follows:
- Surgery should not be considered to be prophylactic for melanoma because a) superficial partial removal (dermabrasion or laser) does not remove the whole lesion b) complete excision is not possible in the group at highest risk of melanoma, and other groups have an extremely low risk c) melanoma can arise outside the CMN, either in a different area of skin or within the CNS
- Most CMN will become lighter spontaneously over the first few years at least, and occasionally this is very dramatic. Serial photographs of CMN should be taken to assess lightening, as both families and physicians can fail to notice this gradual process
- There are some concerns that surgical treatment of the lesions may adversely affect the spontaneous lightening process and the behaviour of the melanocytes in the CMN, although further research needs to be done in to this area
Surgical removal for cosmetic reasons does have a place in the management of CMN, particularly for facial lesions, however
- There is no controlled evidence to support the belief that superficial removal techniques (dermabrasion or laser) need to be performed as early as possible
- There are also concerns about possible adverse effects of early surgery, especially under the age of one year. There is some evidence from other specialities that the use of general anaesthesia in this age group may increase the risk of neurological complications such as cognitive impairment
There is a weekly dedicated clinic for CMN and ther pigmentary abnormalities at the Great Ormond Street Hospital
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Figure 1 – Congenital melanocytic naevus
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Figure 2 – Congenital melanocytic naevus of the abdomen
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Figure 3 – Congenital melanocytic naevus of the thigh
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Figure 4 – Giant congenital melanocytic naevus
Satellite lesions present on bottom
(copied with kind permission of dermatoweb)
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Figure 5 - Giant congenital melanocytic naevus
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Figure 6 - Same patient as figure 5
Satellite lesions on lower legs
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Figure 7 - Same patient as figure 5
Satellite lesions on arms
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Figure 8 - Close up of figure 5
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