RNF43 and colorectal carcinoma: RSPO2 and RSPO3 fusions are mutually exclusive and are present in 2-10% of CRC, co-occurring with KRAS or BRAF mutations, but only very rarely with APC and mutually exclusive of CTNNB1 and RNF43 mutations (Giannakis et al., 2014; Seshagiri et al., 2012; Shinmura et al., 2014).