Congenital Nevomelanocytic Nevus

May 2, 2008
Alexander K. C. Leung, MD
Alexander K. C. Leung, MD

,
Michael Chu, BSc
Michael Chu, BSc

This darkly pigmented lesion on the left arm of a 27-year-old man had been present since birth and had slowly enlarged over the past 2 months. Two days earlier, another physician had diagnosed a wart and treated the lesion with liquid nitrogen, which caused erythema of the surrounding skin.

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This darkly pigmented lesion on the left arm of a 27-year-old man had been present since birth and had slowly enlarged over the past 2 months. Two days earlier, another physician had diagnosed a wart and treated the lesion with liquid nitrogen, which caused erythema of the surrounding skin.

This lesion is a congenital nevomelanocytic nevus. This common hamartoma of the skin is composed of nevocytes that may be present in the dermal-epidermal junction (junctional nevus), in the dermis only (intradermal nevus), or in the junction as well as the dermis (compound nevus).

Congenital nevomelanocytic nevi are present either at birth or within the first few weeks of life. They are distinguished from acquired nevomelanocytic nevi by their larger size, by the lower number of nevi per patient,1 and by their more varied architecture and morphology.2 The incidence in newborns is 0.2% to 2.1%.3 A recent study showed that these nevi tend to follow the lines of Blaschko.4 The "watch and wait" approach is usually adopted for small (less than 1.5 cm) and medium-sized (1.5 to 19.9 cm) nevi.

Giant (greater than 20 cm) congenital nevomelanocytic nevi are of special concern because of their predisposition to the development of melanoma. Furthermore, lesions in the midline in the head and neck may be associated with leptomeningeal melanocytosis, particularly in patients with satellite melanocytic nevi. In this setting, surgical removal of the nevus is indicated. In the absence of leptomeningeal melanosis, prophylactic removal of the lesion is controversial.

The overall risk of a melanoma is low.3 When deciding whether to excise the lesion, cosmetic and psychosocial issues, the potential for malignant transformation, the risk of surgery, and functional outcome must be considered.5 Some experts recommend prophylactic removal of the lesion in toto, with excision into the deep fascia. Other experts recommend superficial excision with regular follow-up. A conservative approach with serial photography of the nevus and follow-up every 6 months for 5 years and every 12 months thereafter has also been advocated.

This patient was reassured of the benign nature of the condition and that no treatment was necessary. However, regular follow-up was recommended.

 

References:

REFERENCES:


1. Leung AK. Obesity and nevocellular nevi. Br J Clin Pract. 1988;42:172-173.
2. Zaal LH, Mooi WJ, Klip H, et al. Risk of malignant transformation of congenital melanocytic nevi: a retrospective nationwide study from the Netherlands. Plast Reconstr Surg. 2005;116:1902-1909.
3. Krengel S, Hauschild A, Schäfer T. Melanoma risk in congenital melanocytic naevi: a systematic review. Br J Dermatol. 2006;155:1-8.
4. Hanayama H, Terashi H, Hashikawa K, et al. Congenital melanocytic nevi and nevus spilus have a tendency to follow the lines of Blaschko: an examination of 200 cases. J Dermatol. 2007;34:159-163.
5. De Raeve LE, Claes A, Ruiter DJ, et al. Distinct phenotypic changes between the superficial and deep component of giant congenital melanocytic naevi: a rationale for curettage. Br J Dermatol. 2006;154:485-492.