GNAQ and primary melanoma of the central nervous system: Activation of mitogen-activated protein kinase (MAPK) has been observed in UM.1 It has been suggested that such activation is mostly due to somatic mutations in GNAQ and GNA11 (GNAQ/11).2, –4 Somatic mutations in GNAQ/11 are reported in more than 80% of the UM tumors.2, , –5 With the exception of blue nevi and melanomas of the central nervous system, somatic mutations in GNAQ/11 are unique to UM and have not been reported in other cancers.6 The mutations in both genes occur mostly in two loci one in exon 4 (codon 183) and the other in exon 5 (codon 209).