RET and medullary thyroid gland carcinoma: Although RET mutations are well described in MTC (Ciampi et al., 2019), there is a paucity of information about RET splice variants in MTC, though one study of a MTC cell line described three splice variants, RET 2/4, RET 2/5, and RET 2/6 and another described functional isoforms RET51 and RET9; however, neither played a role in MTC tumorigenesis (Lorenzo et al., 1995; Mule et al., 2021).