Some people are born with pigmented lesions on the skin. When they are large, they are called giant congenital naevi. They appear as flat pigmented lesions and can be of various sizes. There is usually only one, but occasionally there can be more. As the lesion ages, it may become raised and hairy.
The main clinical concern is whether it will transform into a malignant melanoma. The congenital naevus occurs in 1 to 3% of all newborns. It is usually noted at birth or shortly afterwards. Patients only present to the dermatologist because of cosmetic concerns or melanoma. They can be hairy naevi, but they may also have warning symptoms. Signs of melanoma includes if the mole starts to bleed or grow, or becomes more irregular or change in any way.
Typically, a small congenital naevus requires no investigation. If there is any suspicion of malignant melanoma, a dermatoscopy can be useful. If it is still not conclusive, then a biopsy of the lesion may be used for those more suspicious lesions. If the lesion is small, then an excision biopsy is done. If the mole is larger, then a little chunk is taken. The chunk is removed from the edge towards the centre. This is called a partial or incisional biopsy. Congenital pigmented naevi are associated with neurocutaneous melanosis. For those patients, we advise neuroimaging.
In summary, congenital naevi, pigmented naevus occurs at birth or shortly after. These moles have a lifetime risk of development of melanoma as high as 5 to 7% and the highest risk occurs during childhood or adolescence with a median age of 5 and mean of 15.5 years. Even children and adolescents are at risk of melanoma. This risk is much higher when the congenital melanocytic naevus is of larger size. There is a much smaller risk of malignant transformation in small congenital naevi. Despite the increased risk of melanoma in the larger congenital pigmented naevi, the vast majority of pigmented naevi do not go on to develop melanoma.
If you are concerned about any mole, come and see Dr Jennifer Crawley for your reassurance.