Photos - click on tab labelled Congenital nevus
Congenital nevi, compared to normal skin and compared to banal acquired nevi, are at increased risk for developing melanoma. As a congenital nevus is, essentially, a large accumulation of abnormal melanocytes, this is not unexpected. The risk of melanoma appears to be related to size, i.e. the number of melanocytes. Congenital nevi less than 1 cm diameter appear to have a melanoma risk of less than 1%, whereas nevi of twice the size of the palm probably have a lifetime risk in the order of 5%.
Changes in a congenital nevus that would indicate a potentially worrisome alteration include spatial regression (depressed white areas) and inflammation, as well as a rapidly changing localized colour change or the development of a firm nodule.
Congenital nevi are often excised if small to medium in size. If very large, such as the entire bathing trunk area, excision is practically impossible. In that case yearly review may be indicated. A good close up photograph is often helpful to the patient when doing self examination.
A note on history taking: It is often more useful to ask the patient if they were told that the lesion was present at birth, rather than if the lesion was present at birth. Present since they can remember does not indicate that they have a congenital nevus.
Café au lait lesions (see benign lentigo, click on the tab labelled Lentigo) must be separated from a flat congenital lesion. 26% of children have one café au lait lentigo, whereas only 2% have a congenital nevus. Café au lait lesions have no malignant potential. If in doubt, a small biopsy will define the diagnosis.