Proteins belonging to the same PPIA family (e.g., Prolyl isomerase, Pin1) have been previously demonstrated to be overexpressed in PTC as compared to other thyroid tumours/conditions (medullary thyroid carcinoma, follicular adenoma and goitre [21]), with a subsequent demonstration of a trend in PIN1 expression towards advanced stages of PTC [22]. This evidence concerns the gene PPIA and medullary thyroid gland carcinoma.