Birthmarks: Which ones are worrisome?

San Francisco - Approaching and treating congenital nevocellular nevi (CNN) has always been a tricky task for dermatologists. Is there a risk of transition to malignancy (malignant melanoma), and if yes, when? Does removal of the lesion remove the risk? Are there any prognostic tests? These are just some of the difficult questions dermatologists deal with on a daily basis when confronted with CNN.

Prevalence

Dr. Shwayder cites a prospective study from New York University conducted from 1977 to 1999, where 160 patients were followed for an average of five-and-a-half years, each with a CNN greater than 20 cm in size.

"The study from NYU showed that the five-year cumulative risk of malignant melanoma (MM) is 2.3 percent, and the five year cumulative risk of neurocutaneous melanocytosis (NCM) is 2.5 percent. Patients who developed MM and/or NCM was shown to be 3.3 percent. Also, an increased risk was seen in those patients who had their CNN on a central axial location and/or multiple satellite lesions," Dr. Shwayder explains.

An updated study from Bari Bett, M.D., in the Journal of the American Academy of Dermatology reports the experience of the Nevus Outreach Inc. Web site registry ( http://www.nevus.org/). Of 599 patients with giant garment congenital nevi, 2.9 percent developed melanomas and there have been 0.8 percent deaths to date. The higher risk groups were young in age, had nevi over posterior axes and there was presence of multiple satellites. One of 15 patients with multiple congenital nevi (without one giant one) had melanoma.

Small, but real risk

Dr. Shwayder asserts that removing small congenital nevocellular nevi probably removes the risk of transition to malignant melanoma. He stresses though, that the risk is not zero, and therefore advises the parents that the risk is small but real.

Conversely, removing large congenital nevocellular nevi will probably not affect this risk (2.5 percent to 4 percent of CNN being at risk to turn malignant). He says that transition to malignancy usually occurs in the first three years of life, but can also occur in adulthood.

"Removing a giant CNN is not possible because these nevus cells go very deep, and they will regenerate and repopulate the upper dermis after surgery. Furthermore, most of the risk of malignancy lies in the CNS, not the skin. Also, some anatomic locations where these congenital nevocellular nevi are located are more disquieting than others. The posterior axial, head and neck locations are significantly more worrisome than acral locations," Dr. Shwayder says.

MRI suggested

Dr. Shwayder strongly suggests obtaining an MRI on all large CNN involving the head, neck and spine.

Here, it is important to rule out any neurocutaneous melanocytosis. He stresses that the MRI should be done early (before 4 months of age). If NCM is present with symptoms, the prognosis is usually bad. There is no data to date on the prognosis of NCM without symptoms.

Dr. Shwayder says that at the moment, there are no prognostic tests available for CNN. He stresses that the future belongs to markers and gene rearrangement where ongoing studies and work by Boris Bastian, M.D., have shown much promise.