Quantitative measurements of iodine avidity in surgical specimens (primary tumour and lymph node metastases) of 28 patients were compared to immunohistochemical expression of the thyroid-stimulating hormone receptor, thyroid peroxidase (TPO), pendrin, sodium–iodide symporter (NIS) and mutational status of BRAF and the TERT promoter. This evidence concerns the gene TPO and metastatic malignant neoplasm in the lymph nodes.