NTRK1 and medullary thyroid gland carcinoma: Targeted therapy using the small molecule inhibitors of oncogenic receptor tyrosine kinases or molecular switches has been significantly advanced in recent years for the treatment of surgically incurable progressive thyroid cancers, e.g., RET and VEGF inhibitors for MTC, and B-Raf and MEK1/2 inhibitors for B-RafV600E PTC and ATC.