Melanoma on Congenital Nevi: Case Report

Introduction: Congenital nevi occur in about 1% of newborns. The most used classification is based on their size; small congenital naevus when the largest diameter is less than 1.5cm, intermediate naevi for those between 1.5 and 19.9cm, wide naevus when the diameter is greater than 20cm, and giant naevus when the size is greater than 40cm, with frequent satellite lesions. The risk of transformation into melanoma is estimated at 6.3% for giant nevi, it usually occurs before the age of 20, hence the indication of early excision. This risk is even lower as the size of the nevus is small, and the transformation is usually late. We report the case of a patient with melanoma occurring on a congenital melanocytic naevi of intermediate size. Case Presentation: We report the case of a 54-year-old patient, with no pathological antecedents, who was born with a congenital nevus of the right shoulder with onset 7 months ago of a nodule within the old lesion, increasing rapidly of which the histological study had concluded to a melanoma. Discussion: Melanoma can also occur in congenital nevi less than 10cm in size. They can be considered as precursors of melanoma. Because of their large number and frequency, prophylactic excision of all these nevi is not feasible. However, they should be removed as soon as possible when clinical or dermoscopic changes are observed.