RET and thyroid gland carcinoma: RET fusions have been reported to be involved in the tumorigenesis of thyroid carcinoma through the activation of RET and its downstream pathways such as the phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT) signaling pathway, mitogen-activated protein kinases (MAPK) signaling pathway, and rat sarcoma/extracellular signal-regulated kinase (RAS/ERK) signaling pathway (21, 23-29).