GNA11 and N-RAS mutations: Alternatives for MAPK pathway activating GNAQ mutations in primary melanocytic tumours of the central nervous system

Aim: Primary melanocytic tumours are uncommon neoplasms of the central nervous system. Although similarities with uveal melanomas have been hypothesized, data on their molecular features are limited. Methods: In this study, we investigated the mutational status of BRAF^V600E, KIT, GNAQ, GNA11, N-RAS and H-RAS in a series of 19 primary melanocytic tumours of the central nervous system (CNS). Results: We identified six cases harbouring mutations in the hotspot codon 209 of the GNAQ gene and two cases with mutations in the hotspot codon 209 of the GNA11 gene. Two mutations in codon 61 of N-RAS were also found. In the single strand conformation polymorphism (SSCP) analysis, no shifts corresponding to BRAF^V600E mutations or suggesting activating mutations in the KIT gene were observed. Conclusions: In primary melanocytic tumours of the CNS, GNA11 and N-RAS mutations represent a mechanism of MAPK pathway activation alternative to the common GNAQ mutations. On the other hand, BRAF^V600E mutations and activating KIT mutations seem to be absent or very rare in these tumours.