Congenital Melanocytic Naevus

Definition of a Congenital Melanocytic Naevus

A congenital melanocytic lesion is a black or brown lesion present at birth. A “giant” congenital melanocytic nevus is >20 cm in adults or predicted to reach that size by adulthood¹.

Features of Congenital Melanocytic Naevus

A congential melanocytic naevus presents as a brown or black lesion at birth. It is most commonly found on the trunk and changes appearance over time with multiple satellite lesions.

Natural History

The natural history of giant congenital melanocytic nevi is one of expansion in proportion to the body’s growth.

• At birth: hairless, pale brown, flat lesion
• Colour: hyperpigmentation and colour variegation, surface pigment may fade.
• Texture: hypertrichosis, verrucous, nodularity (neurotisation of the lesion)
• Malignant Transformation: focal growths, ulceration, pruritus, pain, or bleeding

Complications

Complications of giant congenital melanocytic nevi include irritating symptoms (pruritus, ulceration), psychosocial dysfunction related to the aesthetic appearance, and prolonged treatment.

Less common complications include:

• Melanoma: malignant transformation is discussed more below.
• Extracutaneous deposits: mucosal, retroperitoneal, and leptomeningeal.
• Neurocutaneous melanosis: benign or malignant CNS proliferation in patients with giant CMN, multiple satellite lesions and location of trunk or calvarium.
• MSK associations: scoliosis, spinal dysraphism, limb abnormalities.

Melanoma Transformation

Malignant transformation in patients with giant congenital melanocytic nevi can result in cutaneous or noncutaneous melanoma.

The reported risk of melanoma in patients with giant congenital melanocytic nevi ranges from 3-9%² with a lifetime risk of approximately 6% (~ 17-fold increased risk of melanoma compared with the general population)³.

In relation to the rate of malignant transformation^4,5:

• 50% by age 3
• 60% by childhood
• 70% by puberty

For this reason, surgical excision of high-risk cutaneous lesions is best performed in early childhood rather than delaying treatment until a later age.

Management of Congenital Melanocytic Naevus

A multidisciplinary approach involving paediatricians, dermatologists, psychologists, plastic surgeons, neurologists, neurosurgeons, and radiologists.

Active Surveillance

• Regular examination with photography by a dermatologist and plastic surgeons
• Patient education on the natural history and potential for pigment fading.

Surgical Excision

Indications for surgical excision of congenital melanocytic nevi include^6,7:

• Melanoma transformation
• Symptom control
• Maintain function
• Aesthetic improvement

Surgical options include:

• Direct Excision: the most accepted treatment option
• Serial excision: ideally, if amenable to an excision in three stages or less
• Reconstruction: skin graft, expansion, skin substitutes, free tissue transfer.

After surgical treatment, regular follow-up for recurrence and monitoring of satellite lesions.

Timing of Surgery

Early surgery has not been shown to be advantageous and carries increased anaesthetic risk. Surgery can be considered in patients after 1 year when anaesthetic risks are lower.

Traditionally, it was thought that early surgery for CMNs was preferable. This was based on the theory that pigment deepens after birth (‘Abtropfung’⁸). This has now been refuted, and the current theory is that the depth of the naevus correlates best with its size^9-11.

Non-Surgical Options

Many nonsurgical options for the treatment of giant congenital melanocytic nevi have been described, including dermabrasion, laser ablation, curettage, and chemical peel.

Limitations with these treatments include:

• Decrease the burden of nevus cells but do not result in complete cell removal.
• No histologic diagnosis
• Difficult postoperative monitoring for

References

1. Bittencourt, F. V., Marghoob, A. A., Kopf, A. W., et al. Large congenital melanocytic nevi and the risk for development of malignant melanoma and neurocutaneous melanocytosis. Pediatrics 106: 736, 2000.
2. Watt, A. J., Kotsis, S. V., and Chung, K. C. Risk of melanoma arising in large congenital melanocytic nevi: A systematic review. Plast. Reconstr. Surg. 113: 1968, 2004.
3. Rhodes,A.R.,Wood,W.C.,Sober,A.J.,etal.Nonepidermal origin of malignant melanoma associated with a giant con- genital nevocellular nevus. Plast. Reconstr. Surg. 67: 782, 1981.
4. Trozak, D. J., Rowland, W. R., and Hu, F. Metastatic malig- nant melanoma in prepubertal children. Pediatrics 55: 191, 1975.
5. Kaplan, E. N. The risk of malignancy in large congenital nevi. Plast. Reconstr. Surg. 53: 421, 1974.
6. Gosain, A. K., Santoro, T. D., Larson, D. L., et al. Giant congenital nevi: A 20-year experience and an algorithm fortheir management. Plast. Reconstr. Surg. 108: 622, 2001.
7. Bauer, B. S., and Corcoran, J. Treatment of large and giant nevi. Clin. Plast. Surg. 32: 11, 2005.
8. Unna PG. Naevi und Naevocarcinome. Berl Klin Wochenschr 1893;30:14e6.
9. Worret WI, Burgdorf WH. Which direction do nevus cells move?Abtropfung reexamined. Am J Dermatopathol 1998;20:135e9
10. Barnhill RL, Fleischli M. Histological features of congenital melanocytic nevi in infants one year of age or younger. J Am AcadDermatol 1981;33:780e5.
11. Cass DL, Bullard KM, Sylvester KG, et al. Wound size and gestational age modulate scar formation in fetal wound repair. J Pediatr Surg 1997;32:411e5.
12. Kinsler, V., & Bulstrode, N. (2009). The role of surgery in the management of congenital melanocytic naevi in children: a perspective from Great Ormond Street Hospital. Journal of Plastic, Reconstructive & Aesthetic Surgery, 62(5), 595–601.doi:10.1016/j.bjps.2008.12.016 10.1016/j.bjps.2008.12.016