Mutational dichotomy in desmoplastic malignant melanoma corroborated by multigene panel analysis

Area of Science:

• Oncology
• Dermatology
• Genetics

Background:

• Desmoplastic melanoma is a distinct subtype with pure and mixed forms.
• Pure desmoplastic melanoma shows fewer lymph node metastases than the mixed form.
• Common driver mutations (BRAF, NRAS, KIT) are typically absent in pure desmoplastic melanoma.

Purpose of the Study:

• Investigate alternative driver mutations in desmoplastic melanoma.
• Compare mutation profiles between pure and mixed desmoplastic melanoma subtypes.
• Identify potential therapeutic targets based on genetic alterations.

Main Methods:

• Next-generation amplicon sequencing of 50 tumorigenesis-related genes.
• Investigation of the RET G691S polymorphism.
• Analysis of mutation status in 21 desmoplastic melanoma samples (12 pure, 9 mixed).

Main Results:

• Pure desmoplastic melanomas were often mutation-devoid (50%) or had tumor suppressor gene mutations (TP53, CDKN2A, SMAD4).
• Mixed desmoplastic melanomas frequently harbored activating mutations (89%), including BRAF, NRAS, FGFR2, and ERBB2.
• The RET G691S polymorphism was present in 25% of pure and 38% of mixed cases.

Conclusions:

• Pure desmoplastic melanoma lacks activating driver mutations beyond those previously studied.
• Mixed desmoplastic melanoma shares activating mutations with common cutaneous melanomas.
• Findings support a therapeutic dichotomy between pure and mixed desmoplastic melanoma based on mutation status.