Children can be born with pigmented moles called congenital nevi (or nevus, if one). These symbolize an increase of melanocytes, the pigment-producing cells of the skin. When they are present at birth, they can be highly varied in size and shape. They may be very small and of no consequence in looks to very huge, covering large areas of the body. Small congenital nevi are those less than 1.5 cm in size. Giant nevi are those measured 20cm or more in size at birth. The goal of giant nevi removal surgery is to remove the mole in its entirety or at least as much as is possible.
Congenital nevi are believed to have an increased risk of malignant transformation over the lifetime of the child. Small- and medium-sized congenital melanocytic nevi have a risk as low as 1% or less. Large and giant melanocytic nevi have a higher risk of 5-10% over the child's lifetime. As the child reaches puberty, congenital melanocytic nevi can develop additional changes creating a worsened appearance due to thickening, darkening, or ulcerations of any part of the entire lesion.