Investigation into the mechanism(s) of resistance is largely limited by the number of genes in each genetic testing panel; various approaches have been taken, including a melanoma-specific multiplex mutational profiling assay developed to detect 43 recurrent mutations occurring in six genes frequently mutated in melanomas (BRAF, NRAS, KIT, GNAQ, GNA11, and CTNNB1; ref. 17). The gene discussed is CTNNB1; the disease is melanoma.