RET and differentiated thyroid carcinoma: In vitro evidences show that mitogen-activated protein kinase (MAPK) inhibitors have a stronger effect against medullary thyroid carcinoma (MTC) human cancer cell lines, carrying point mutated isoforms of the RET kinase, than against a papillary thyroid carcinoma (PTC) human cancer cell line, carrying the CCDC6-RET fusion [90].