Whereas Ki-67 mRNA expression levels were similar for PTC (median dCT value: 31.9), FTC (median dCT value: 31.6), and MTC (median dCT value: 31.5), significantly higher values were observed for ATC (median dCT value: 35.4) (pairwise Mann-Whitney tests vs. ATC: p ≤ 0.001). This evidence concerns the gene MKI67 and medullary thyroid gland carcinoma.