FGFR1 and differentiated thyroid carcinoma: A couple of non-FGFR1-derived circRNAs have been reported to promote FGFR1 expression, such as circ_SNX27 [18] and circRAPGEF5 [19], which functioned as miRNA sponges for miR-637 (in hepatocellular carcinoma) and miR-198 (in papillary thyroid carcinoma) respectively.