You are called to the newborn nursery to evaluate a healthy vigorous newborn with a large dark brown area on the back of the scalp and neck. The anxious first-time parents are tapping on the nursery window as you examine the child. What's the diagnosis
Diagnosis and Clinical Presentation
Diagnosis: Congenital Melanocytic Nevi (CMN) Congenital melanocytic nevi are present at birth and are immediately evident or appear within the first few months of life. These lesions are composed of nevomelanocytic cells derived from the neural crest. CMN are thought to occur when there is an error in migration of the neuroectodermal cells early in development. This results in arrest of melanoblasts along their route from the neural crest to various sites in the body, differentiation into dendritic melanocytes, and dysregulated growth of these cells which occurs in utero between the 5th to 24th week of gestation (1,2). CMN are present in approximately 1% of newborns; however; large lesions measuring greater than 10 cm are found in only 1/20,000 live births (1-3). The most widely accepted classification of CMN is according to size. Small CMNs are defined as measuring less than 1.5cm, medium are 1.5 to 19.9cm, and large or giant are greater than 20 cm (3). A CMN is also considered large if it affects a significant portion of an anatomical area, it is predicted that it will reach 20cm by adulthood, or if the nevus covers greater than 1% of the total body surface area in the head or neck or 2% elsewhere in the body (2). This distinction may be as important as the size of the CMN when discussing treatment and prognosis (3). Congenital melanocytic nevi are diagnosed clinically by their size (even small lesions are usually bigger than acquired nevi) round to oval configuration, increased coarse dark hair and smooth, regular well demarcated borders. The clinical appearance may evolve with age and is variable in each individual. In neonates leathery plaques in shades of brown or black are typical, but variable blue, red or pink shades may be present. Although many nevi will darken somewhat during infancy, many will lighten as they become rougher, more elevated and/or warty in texture in toddlers and school age children (6). Parents are often particularly worried about increasing coarse and dark hair and the development of variably pigmented papules, nodules and plaques in medium size and large nevi.
Epidemiology and pathogenesis
Large congenital melanocytic nevi (LCMN) have occasionally been reported in association with scoliosis, spina bifida, clubfoot, cranial bone hypertrophy and neurofibromatosis (4). However, most children do not have associated findings. Although the lifetime risk of melanoma in patients with LCMN is unknown, recent figures of 2.5-5% (in comparison of old literature suggesting a risk approaching 50%) seem reasonable (7). However, the risk may actually be lower, because of biases inherent in collecting data on these individuals. Some investigators have reported that the greatest risk is within the first 5 years of life with 50% developing by three to five years of age and seventy percent before the age of 10. Data from the New York University-LCMN Registry have demonstrated that all patients who developed malignant melanoma had LCMN in an axial location. No malignant melanomas were found in LCMN on the extremities or arising from satellite lesions. Some studies have demonstrated a statistical significant association between a large number of satellite lesions, defined as greater than ten, and the risk of developing malignant melanoma. Neurocutaneous melanosis (NCM) or leptomeningeal melanocytosis (LM) is a rare complication of LCMNs in which there is an abnormal proliferation of melanocytes in the leptomeninges. Melanoma may develop in the central nervous system when these melanocytes undergo malignant degeneration. Signs and symptoms of NCM may be due to increased intracranial pressure, mass lesions or spinal cord compression and include abnormal reflexes, hydrocephalus and papilledema. (4,8). Most patients who present with NCM have LCMN in a posterior axial location with involvement of the head, neck, and/or trunk, and have numerous satellite lesions. Cerebrospinal cytology and magnetic resonance imaging (MRI) with gadolinium contrast enhancement are the most sensitive studies to diagnose NCM. MRI screening should be performed between 4-6 months of age when the anesthesia risks are decreased and before normal myelination of the brain obscures melanin deposits. (1) The psychosocial impact on parents and eventually patients diagnosed with LCMN results from a combination of disfigurement from the skin lesions, anxiety regarding the risk of complications and discomfort caused by surgery. While the primary goal of treating LCMNs in early childhood is directed at decreasing the risk of developing melanoma, the removal or reduction of the disfiguring lesions will also help support the child’s self image when they enter the preschool years. However, surgery should be individualized, and it is important to point out to parents that no studies have demonstrated that surgery decreases the risk of malignant change. As a consequence, parents should be reassured that extensive, complex surgical procedures may not be in the child’s best interest (2). Many congenital nevi will be camouflaged by hair and other normal structures, so surgical intervention may not be necessary for a good cosmetic outcome.
Café au lait macules are uniformly pigmented and flat as are lentigines. Transient neonatal pustular melanosis (TNPM) can result in dramatic freckling in characteristic areas on the torso. However the pigmented macules in TNPM often have surrounding peeling scale initially and then salt and pepper-like pigmentation which disappears within the first few weeks of life. Epidermal nevi tend to be warty and uniformly brown in color and follow the lines of Blaschko. Nevus sebaceous in dark pigmented individuals may be confused with nevocellular nevi in the newborn, but sebaceous nevi tend to be yellow-orange in color and have a smooth waxy surface. Vascular malformations in dark pigmented infants can usually be distinguished by the purple-red color which blanches with pressure.
The management of a patient with a large congenital melanocytic nevus is complex and must be individualized to each patient. In determining the appropriate course of action the size, location of the lesion, age of the patient, cosmetic outcome, surgical complexity, anesthetic risk and the perceived danger of developing associated problems such as neurocutaneous melanosis and malignant melanoma must be weighed. (4,8). A multidisciplinary approach is appropriate as the child should be evaluated by a pediatrician, dermatologist, plastic surgeon, neurologist, neurosurgeon, radiologist and psychologist. Regular examinations every 6 months during the first year of life or longer in children with axial lesions and yearly in older children or those with smaller lesions should be performed by practitioners comfortable with the management of LCMN. Skin biopsy of suspicious changes within the nevi should be performed and coordinated with surgical management. The use of magnetic resonance imaging or computed tomographic scans for routine follow-up and detection of melanoma has not been shown to be effective and should only be used in a research setting or when indicated by clinical findings.
Our patient was healthy without other anomalies, and we elected to monitor the child clinically. We did, however, have him evaluated by pediatric plastic surgery for discussion of possible excision or partial excision of the nevus in the future.
Congenital pigmented nevi require careful evaluation, ongoing monitoring, and consideration of surgical excision when indicated.
- 1. Marghoob, Ashfaq M.D. Congenital melanocytic nevi: Evaluation and Management. Dermatol Clin 20 (2002) 607–616. 2. Arneja, Jugpal S. M.D.; Gosain, Arun K. M.D. Giant Congenital Melanocytic Nevi. Plastic and Reconstructive Surgery. Issue:Volume 120(2), August 2007, pp 26e-40e 3. Precursors to Malignant Melanoma. NIH Consens Statement 1983 Oct 24-26;4(9):1-14. 4. Zeina S. Tannous, MD, Martin C. Mihm, Jr, MD, Arthur J. Sober, MD, and Lyn M. Duncan, MD. Congenital melanocytic nevi: Clinical and histopathologic features, risk of melanoma, and clinical management. J Am Acad Dermatol. Vol. 52 Issue 2. February 2005. pp 197-203. 5. E.K. Hale, J. Stein, et al. Association of melanoma and neurocutaneous melanocytosis with large congenital melanocytic naevi—results from the NYU–LCMN registry. E.K. Hale, J. Stein, et al. British Journal of Dermatology 2005 152, pp512–517. 6. Habif, Thomas P., Clinical Dermatology: A color guide to diagnosis and therapy. 4th Edition. 7. Schaffer, J.V., Bolognia J.L (2008) Congenital melanocytic nevi and speckled lentiginous nevi. In M.L. Levy (Ed.), UpToDate. Available from http://www.uptodateonline.com. 8. DeDavid, M. Neurocutaneous melanosis: clinical features of large congenital melanocytic nevi in patients with manifest central nervous system melanosis. J Am Acad Dermatol . Oct-1996; 35(4): 529-38.