Additionally, HER2 IHC scores, using either the ASCO/CAP34,35 or Peña36 guidelines (Supplementary Fig. 3), were statistically different between FTC and MTC (Mann-Whitney, p = 0.0007), with all MTC tumors considered HER2 negative (scores 0/1) while FTC spanned the entire score range (0–3). This evidence concerns the gene ERBB2 and medullary thyroid gland carcinoma.