Congenital Giant Melanocytic Nevus

Langley AFB Pediatrics

Deepak M. Kamat, MD, PhD––Series Editor: Dr Kamat is professor of pediatrics at Wayne State University in Detroit. He is also director of the Institute of Medical Education and vice chair of education at Children’s Hospital of Michigan, both in Detroit.

Congenital Giant Melanocytic Nevus

The skin lesions on this infant girl had been present since birth; she is shown here at approximately 2 weeks of age (A). Results of the physical examination were completely normal except for the lesions, which demonstrated the classic “swim-trunk” contiguous circumferential nevus distribution from the upper third of the thighs to just below the nipple line. The surface texture varied from smooth to warty, and the color ranged from brown to bluish black. Some fine, dark vellus hair was noted on the lower lumbar region. The spine exhibited no abnormalities other than the nevus. Also noted were fewer than 10 discrete satellite lesions, which were less than 1 cm in diameter; these were near but not contiguous with the large nevus.

Pregnancy and delivery were unremarkable. The child’s siblings have no significant nevi; however, the mother does have at least one large, dark, hairy nevus of less than 6 cm, possibly from birth. In addition, a maternal uncle reportedly has several large, hairy nevi thought to be present from birth.

At least two dermatology consultations were obtained; the diagnosis was confirmed as congenital giant melanocytic nevus, which is also known as giant hairy nevus or bathing trunk nevus. Multiple intralesional biopsies demonstrated typical melanocytic and occasional neural supportive elements. MRI scans of the child’s brain and spine performed during the first 3 months of life were interpreted as normal.

Congenital giant melanocytic nevi are uncommon in the pediatric population. Although the risk of malignant transformation associated with these lesions has been well established, management strategies remain controversial. Lesions at highest risk for malignant transformation are those that occur on the trunk; the risk is estimated to be about 2.5% to 5%. More than half of patients in whom malignant melanoma develops in giant congenital nevi are younger than age 10.1

Patients with large congenital melanocytic nevi are also at significantly increased risk for the development of neurocutaneous melanosis (NCM), which may result in neurologic and neurodevelopmental sequelae as well as an elevated lifetime risk of central nervous system melanoma. Signs of NCM include hydrocephalus, macrocephaly, increasing head circumference, bulging fontanelle, seizures, and developmental delay. Symptoms of NCM may include headache vomiting, failure to thrive, weakness, gait abnormalities, and/or bladder or bowel dysfunction.

Congenital Giant Melanocytic Nevus

Treatment options for large congenital melanocytic nevi vary widely; they range from surveillance alone, surveillance with biopsies, and dermabrasion (which some reasearchers have suggested may increase malignant transformation) to the use of expanded flaps, expanded full-thickness skin grafts, split-thickness or non-expanded full-thickness skin grafts, and serial excision.

This patient is now a toddler and has no signs of NCM. She is doing well from the standpoint of growth and development. She has had multiple tissue expanders placed for later harvest of unaffected skin for use in grafting onto large excised affected skin areas (B). Much affected skin remains, and long hair has developed in most of these areas. The patient and her family have faced and overcome significant challenges during this course of therapy. The decision to use serial tissue expanders followed by excision and grafting was made to decrease as much as possible the absolute malignant potential, as well as to improve cosmesis.