Abstract
Papillary and follicular thyroid carcinomas (PTC and FTC) are prominent malignancies that originate from thyroid follicular cells. PTC is usually diagnosed via preoperative cytology, and large tumor size, clinical node metastasis, and distant metastasis constitute preoperative prognostic factors. Gross extrathyroidal and extranodal tumor extensions have a significant prognostic impact, are evaluated intraoperatively, and are useful for determining the extent of surgery. Aggressive variants, such as tall cell and hobnail variants, a high Ki-67 labeling index (LI), and somatic gene mutations are prognostic factors in postoperative pathological and molecular examinations. In contrast, FTC is generally diagnosed based on postoperative pathology. Large tumor size and M factors have prognostic value; however, the findings of pathological examinations are very important. FTCs are classified as minimally invasive, encapsulated angioinvasive, and widely invasive FTCs. Widely invasive FTC with vascular invasion (VI) and encapsulated angioinvasive FTCs with extensive VI have a poor prognosis, whereas widely invasive FTC without VI has an excellent prognosis, which is similar to that of minimally invasive FTC. This indicates that VI is a considerably more important prognostic marker than capsular invasion. For postoperative follow-up, dynamic markers such as the thyroglobulin-doubling rate (DR), metastatic tumor volume-DR, and change in the neutrophil-to-lymphocyte ratio are important and are useful for evaluating the effectiveness of treatments, such as radioactive iodine therapy and molecular targeted therapy, for recurrent lesions. For clinicians, it is important to accurately evaluate prognostic markers of PTC and FTC in the pre-, intra-operative, and post-operative phases.