FGF4 and neoplasm: Interestingly, in both cases, the copy of FGF4 expressed and involved in the fusion was the one closer to ANO1. Similarly, among the other quadruple WT samples, it was possible to identify two informative heterozygous SNPs at the DNA level located in UTR regions of FGF4 that were monoallelically expressed in two cases (GIST127 and GIST133) (Fig. 2C), indicating that FGF4 expression was derived from only one copy of FGF4 also in these tumours.