This inability of cancer cells to absorb iodine results from theloss of thyroid differentiation, which is directly associated with MAPK activationand is seen more often in tumors with BRAF mutations than in tumors with othermutations (such as receptor tyrosine kinase [RTS]) (26), indicating the need for molecular targetedtherapeutic options in RAI-refractory thyroid cancer. The gene discussed is NTRK1; the disease is cancer.