What is giant nevi removal surgery?

Children can be born with pigmented moles called congenital nevi (or nevus, if singular). These represent a proliferation of melanocytes, the pigment-producing cells of the skin. When they occur, congenital melanocytic nevi can be highly varied in size and shape. They may be very small and insignificant in appearance to very big, covering large areas of the body. Small congenital nevi are those less than 1.5cm in size. Giant nevi are those measuring 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.

Cause and presentation of giant nevi

A congenital nevus, including giant nevi, are generally considered to occur sporadically, in a completely unpredictable fashion. Small congenital nevi are seen in 1 in 100 births whereas giant nevi occur much more infrequently – 1 in 20,000 births. These moles (also known as melanocytic nevi) are usually brown in color. That color may be uniform or very irregular with darker areas mixed with lighter areas. Congenital nevi can also have thickened or raised areas, texture differences and excessive hair growth. Because excess hair growth is common, these lesions are sometimes alternately referred to as giant hairy nevi. While giant congenital nevi can occur at any body site, there is a predilection for them to appear on the trunk, including back, abdomen, hips and buttocks. The scalp and face are also frequently involved.

Rarely, some children born with giant congenital nevi are found to have deeper involvement of their tissues called neurocutaneous melanosis. The melanocytes involved in this condition proliferated in the brain and spinal cord early in fetal development and typically present with a giant scalp or trunk lesion and many smaller satellite lesions. These children can suffer from increased intracranial pressure, seizures or other neurological problems. An MRI can help to diagnose this condition if it is suspected.

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 or all of the lesion.

Giant nevi can be challenging to effectively manage. There is often a sense of urgency to remove the external lesion for both medical and cosmetic reasons. The large size of these lesions means they usually cannot be removed all at once in order to allow for primary healing of the excised areas. Many techniques have been developed to provide adequate tissue for closure of the surgical wound that is created by removing the nevi. Most commonly this includes tissue expansion and grafting.