Rapidly Involuting Congenital Melanocytic Naevi in Two Children

Congenital melanocytic naevi (CMN) are considered to be neural crest-derived hamartomas, which are visible at, or shortly after, birth as pigmented tumours (1). The incidence of any size of CMN of neonates ranges from 0.2 to 2.1% (2, 3). They are categorized according to the maximum diameter that the naevus will achieve; small ( 10–20 cm) and giant (> 20 cm) (4). In addition to the cosmetic concern, CMN pose several problems, such as neurocutaneous melanosis, and risk of malignant transformation (5, 6). In a systematic review the risk of melanoma in CMN was estimated to be 0.7%, with a higher risk of malignant transformation occurring during childhood and adoles-cence for giant CMN (2, 7, 8). CMN have a dynamic course and may change over time. They can increase in size during childhood, be-come darker in colour, become hairy, or show pigmen -tary regression (9). Spontaneous involution is a rare phenomenon with few cases described in the literature and, when it occurs, it is often associated with a hypo- or de-pigmented halo (6, 9, 10). We report here 2 cases of spontaneous rapid involution without the halo pheno-menon, in medium to large CMN in 2 children referred to the Karolinska University Hospital.CASE REPORTS