Mutational status of naevus-associated melanomas

Area of Science:

• Oncology
• Genetics
• Dermatology

Background:

• The origin of melanoma, particularly its relationship with melanocytic nevi, remains a subject of debate.
• Previous studies suggest melanomas can arise de novo or from a pre-existing nevus.

Purpose of the Study:

• To investigate the mutational profiles of genes involved in melanomagenesis within a large cohort of naevus-associated melanomas.
• To determine the clonal relationship between melanomas and their adjacent nevi at a molecular level.

Main Methods:

• Sixty-one naevus-associated melanomas underwent microdissection and Sanger sequencing of key genes (BRAF, NRAS, c-KIT, PPP6C, STK19, RAC1).
• Mutations were confirmed using rigorous methods, including allele-specific PCR, capillary electrophoresis, and SNaPshot analysis, ensuring high accuracy.

Main Results:

• A significant majority (66.7%) of melanomas and their associated nevi exhibited concordant mutational status across the analyzed genes.
• Concomitant mutations in BRAF and NRAS were observed in nine cases, with one instance of double mutations in both melanoma and nevus.
• BRAF mutations were identified in melanomas and associated nevi on acral sites, including an acral lentiginous melanoma.

Conclusions:

• This study represents the largest molecular analysis of naevus-associated melanomas to date.
• The shared mutational profiles between melanomas and adjacent nevi provide strong evidence for a clonal relationship.
• Findings support the hypothesis that melanoma originates within a pre-existing melanocytic nevus.