FGFR4 and cancer: The irregular expression of the FGFR4 pathway may be induced by gene amplification, posttranscriptional errors (Helsten et al., 2016), FGFR4 mutations (Futami et al., 2019), translocations, isoform switching, alternative splicing of FGFR4 (Kwiatkowski et al., 2008), and overexpression of specific ligands in cancer or stromal cells (Miura et al., 2012).