Which mutation is most commonly found in melanoma?

• A. NRAS mutation
• B. BRAF V600 mutation
• C. KIT mutation
• D. PTEN loss

Answer: (B)

Activating mutations in the MAPK signaling pathway are common in melanoma, and the most frequent event is a substitution at BRAF codon 600. The BRAF V600E mutation makes the BRAF kinase constitutively active, driving continuous MEK-ERK signaling and promoting melanoma cell growth without needing upstream signals. Because this mutation appears in roughly half of melanomas, it defines the dominant molecular subset and explains why targeted therapies against BRAF (often with MEK inhibitors) are effective. Other mutations like NRAS occur less often, KIT mutations are relatively rare and tied to specific melanoma subtypes, and PTEN loss is a tumor suppressor change that doesn’t account for the majority of cases.