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When Is MRI Useful in Managing of Congenital Melanocytic Nevi?

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When used for appropriate patients, MRI imaging is helpful in congenital melanocytic nevus (CMN) management and may help predict neurologic outcomes or drive neurosurgical intervention, results from a small multi-institutional study showed.



Holly Neale

“The majority of congenital nevi are considered low risk for cutaneous and/or systemic complications,” Holly Neale said at the annual meeting of the Society for Pediatric Dermatology. “However, a subset of children born with higher-risk congenital nevi require close monitoring, as some features of congenital nevi have been associated with cutaneous melanoma, central nervous system melanoma, melanin in the brain or spine, and structural irregularities in the brain or spine. It’s important to understand which congenital nevi are considered higher risk in order to guide management and counseling decisions.”

One major management decision is to do a screening magnetic resonance image of the CNS to evaluate for neurologic involvement, said Neale, a fourth-year medical student at the University of Massachusetts, Worcester. Prior studies have shown that congenital nevi that are bigger than 20 cm, posterior axial location, and having more than one congenital nevus may predict CNS abnormalities, while recent guidelines from experts in the field suggest that any child with more than one congenital nevus at birth undergo screening MRI.

“However, guidelines are evolving, and more data is required to better understand the CNS abnormalities and patient outcomes for children with congenital nevi,” said Neale, who spent the past year as a pediatric dermatology research fellow at Massachusetts General Hospital, Boston.

To address this knowledge gap, she and colleagues at the University of Massachusetts, Massachusetts General Hospital, and Boston Children’s Hospital performed a retrospective chart review between Jan. 1, 2009, and Dec. 31, 2019, of individuals ages 18 and younger who had an MRI of the brain or spine with at least one dermatologist-diagnosed nevus as identified via key words in the medical record. Of the 909 patients screened, 46 met inclusion criteria, evenly split between males and females.

The most common location of the largest nevus was the trunk (in 41% of patients), followed by lesions that spanned multiple regions. More than one-third of patients had giant nevi (greater than 40 cm).

“The majority of images were considered nonconcerning, which includes normal, benign, or other findings such as trauma related, infectious, or orthopedic, which we did not classify as abnormal as it did not guide our study question,” Neale said. Specifically, 8% of spine images and 27% of brain images were considered “concerning,” defined as any finding that prompted further workup or monitoring, which includes findings concerning for melanin.

The most common brain finding was melanin (in eight children), and one child with brain melanin also had findings suggestive of melanin in the thoracic spine. The most common finding in spine MRIs was fatty filum (in four children), requiring intervention for tethering in only one individual. No cases of cutaneous melanoma developed during the study period, and only one patient with abnormal imaging had CNS melanoma, which was fatal.

All patients with findings suggestive of CNS melanin had more than four nevi present at birth, which is in line with current imaging screening guidelines. In addition, children with concerning imaging had higher rates of death, neurodevelopmental problems, seizures, and neurosurgery, compared with their counterparts with unremarkable imaging findings. Describing preliminary analyses, Neale said that a chi square analysis was performed to test statistical significance of these differences, “and neurosurgery was the only variable that children with concerning imaging were significantly more likely to experience, although sample size limits detection for the other variables.”

The authors concluded that MRI is a helpful tool when used in the appropriate clinical context for the management of congenital nevi. “As more children undergo imaging, we may discover more nonmelanin abnormalities,” she said.

Joseph M. Lam, MD, who was asked to comment on the study, said that the increased risk of CNS melanin in patients with larger lesions and in those with multiple lesions confirms previous reports.

“It is interesting to note that some patients with nonconcerning imaging results still had neurodevelopmental problems and seizures, albeit at a lower rate than those with concerning imaging results,” said Lam, a pediatric dermatologist at British Columbia Children’s Hospital, Vancouver. “The lack of a control group for comparison of rates of neurological sequelae, such as NDP, seizures and nonmelanin structural anomalies, limits the generalizability of the findings. However, this is a nice study that helps us understand better the CNS anomalies in CMN.”

Neale acknowledged certain limitations of the study, including the lack of a control group without CMN, the small number of patients, the potential for referral bias, and its retrospective design. Also, the proximity of the study period does not allow for chronic follow-up and detection of the development of melanoma or other problems in the future.

Neale and associates reported having no relevant financial disclosures. Lam disclosed that he has received speaker fees from Pierre Fabre.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.

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