Ailesbury Clinic Cases
Giant congenital melanocytic nevus diilemma
A 40yo Indian male presented with a large congenital nevus covering most of his lower body. The naevus measured 35 cm x 20 cm with a flat mammilated surface, well-demarcated borders and some degree of hypertrichosis. Dermoscopic examination showed coarse pigment in the darker centre of the naevus and deeper pigmentation around its periphery. The patient said that over time, it had become darker with an increase in hair growth, and it had acquired a more irregular surface.
Congenital melanocytic nevus (CGN) before treatment with CO2 laser
It had a major psychological effect on the patient and he felt it had prevented him finding a mate. The patient was aware of the possibility of developing melanoma, within the lesion. Although the value of the incidence rate of malignancies in GCMN may still be a matter of dispute, it is estimated that for these individuals the lifetime-risk for developing melanoma is between 5 and 10%. Another doctor in India had commenced the treatment but referred him to my clinic as we had a more powerful CO2 laser.
Congenital melanocytic nevus (CGN) is primarily a clinical diagnosis. It is usually defined as a melanocytic lesion present at birth that will reach a diameter ≥ 20 cm in adulthood. Its incidence is estimated in <1:20,000 newborns (1) (2). Despite its rarity, this lesion is important because it may associate with severe complications such as malignant melanoma, affect the central nervous system and have major psychosocial impact on the patient and his family due to its unsightly appearance (3) (4).
However, congenital nevi are histologically distinguished from acquired nevi mainly by their larger size, the spread of the nevus cells to the deep layers of the skin and by their more varied architecture and morphology. Although giant congenital melanocytic nevus is recognized as a risk factor, the risk of malignant melanoma in congenital melanocytic naevi (CMN) is a matter of ongoing debate. In one study, fourteen articles were chosen for further analysis.
The studies varied significantly with respect to study design (source of cases; retrospective vs. prospective analysis), age of patients, follow-up time, and nevus characteristics. The overall risk of melanoma of 0.7% in all 14 studies (5). Although satisfying to this author, this was lower than many other studies that show the estimated lifetime risk of developing melanoma varies from 5 to 10% (6). On account of these uncertainties and the size of the lesions, the management of giant congenital melanocytic nevus needs individualization (7).
The issue of deciding which is the best therapeutic approach in these cases also causes distress to the medical team, due to the controversies surrounding the treatment of these lesions - which stems largely from the uncertainties about the risks of complications (8). Treatment may include surgical and non-surgical procedures, psychological intervention and/or clinical follow-up, with special attention to changes in color, texture or on the surface of the lesion. The only absolute indication for surgery in giant congenital melanocytic nevus is the development of a malignant neoplasm on the lesion (9). GCMN diagnosis is mainly clinical. From the histological standpoint, however, CMN is generally differentiated from acquired nevus mainly by its larger size, the dissemination of nevus cells into the deeper layers of the skin (including subcutaneous tissues) and its varied architecture and morphology (10).
When melanoma arises in GCMN, the prognosis is poor. One of the reasons is the fact that cutaneous melanoma associated with GCMN typically grows in the dermis and this makes it more difficult to detect in clinical exams. More than half of the patients will die within three years and the median age at death is 4.5 years (11). Prophylactic surgical excision is justified based on the assumption that melanoma may arise on the nevic lesion. However, 50% of melanomas found in patients with GCMN occur elsewhere and the removal of the nevus does not guarantee protection against malignancy (12). It is logical to assume the reduction of melanocytic cells reduces the incidence of malignancy. However, the partial removal of GCMN by procedures such as fractionalised CO2 laser treatment has only cosmetic purposes, since only the most superficial cells of the lesion are removed (13).
The use of CO2 laser in the treatment of GCMN remains controversial as there is some concern that nevus cells exposed to doses of energy may have a higher probability of malignant transformation (14). There is also a suspicion whether laser surgery that partially removes congenital pigmented lesions could impair or facilitate the detection of abnormalities suggestive of melanoma on the nevus (15). There is also the counter-argument that reducing the overall number of melanocytic cells can only reduce the risk of these turning malignant.
Congenital melanocytic nevus (CGN) after treatment with CO2 laser
However, these effects must be balanced against the psychological impact that the lesion has on the patient as there is no doubt that CO2 laser can dramatically improve the gross aesthetic appearance of these lesions.
1. Wu D, Wang M, Wang X, Yin N, Song T, Li H, et al. Lack of BRAF(V600E) mutations in giant congenital melanocytic nevi in a Chinese population. Am J Dermatopathol. 2011;33:341–344.
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3. Kovalyshyn I, Braun R, Marghoob A. Congenital melanocytic naevi. Australas J Dermatol. 2009;50:231–240.
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9. Giant congenital melanocytic nevus Ana Carolina Leite Viana, Bernardo Gontijo, and Flávia Vasques Bittencourt An Bras Dermatol. 2013 Nov-Dec; 88(6):863-878.
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14. Michel JL. Laser therapy of giant congenital melanocytic nevi. Eur J Dermatol. 2003;13:57–64
15. Bohn J, Svensson H, Aberg M. Dermabrasion of large congenital melanocytic naevi in neonates. Scand J Plast Reconstr Surg Hand Surg. 2000;34:321–326