Unveiling Birthmark Melanoma Risks: A Comprehensive Analysis of Congenital Melanocytic Nevi of All Sizes

Original Article: Risk of melanoma in congenital melanocytic nevi of all sizes: A systematic review

What are the key takeaways of this article?

Congenital melanocytic nevi (CMN) are benign proliferations of melanocytic cells that are present at birth or arise in the first weeks of life. While these lesions are commonly encountered in newborns, they can be classified based on their projected adult size. The classifications include small (<1.5 cm), medium (1.5 to <20 cm), large (20 to <40 cm), and giant (≥40 cm), with consideration of characteristics such as localization, color, and hypertrichosis. While larger CMN are associated with a higher lifetime risk of developing melanoma, the level of risk remains unclear for small or medium-sized CMN.

As such, this systematic review and meta-analysis aimed to assess the risk of melanoma in patients with CMN of all sizes. The study includes prospective and retrospective observational studies that recruited patients of any age with ≥1 CMN and evaluated cases of melanoma. The study recruited a total of 7915 patients and found a reported prevalence of 1.15% of melanomas in the entire study population, with an overall incidence density of 0.057% person-years. The authors reported a higher risk (RR= 21.9 (95% CI, 8.55–56.3)) of melanoma incidence densities in large to giant CMN compared to small to medium CMN at 15 years of age. Additionally, the incidence density was higher in CMN located on the trunk and in those left untreated or partially treated compared to complete excision.

The review discusses the main concern in the management of CMN, which is the risk of developing melanoma, especially for larger CMN. The prevalence of CMN is estimated to be between 1% and 4% in newborns, with larger CMN being less common. The study found that patients with CMN of medium, large, and giant size are at risk of melanoma, while the risk remains unknown for small CMN. Several limitations were identified, including selection biases, heterogeneous study designs and follow-up durations, insufficient data on small CMN, and challenges in assessing the risk of melanoma prevention with complete excision. These findings suggest that complete excision of CMN may reduce the risk of melanoma, however the efficacy of prophylactic surgery in preventing melanoma remains uncertain.

Overall, this study provides valuable insights into the risk of melanoma in patients with CMN of all sizes, highlighting the need for further research, longer-term follow-up studies, and national registries to better understand and manage the risk of melanoma associated with CMN.

Publication Date: February 4th, 2024

Reference: Scard C, Aubert H, Wargny M, Martin L, Barbarot S. Risk of melanoma in congenital melanocytic nevi of all sizes: A systematic review. Acad Dermatol Venereol. 2023;37(1):32-39. doi:10.1111/jdv.18581

Summary By: Megan Lowe