Prognostic factors evaluated in differentiated thyroid carcinomas.

Differentiated thyroid carcinoma includes papillary (PTC) and follicular thyroid carcinomas (FTC). The biological characteristics and prognostic factors of these two carcinomas differ significantly. PTC is generally diagnosed by cytology; large tumor size, clinical node metastasis, and gross extrathyroidal and extranodal tumor invasion are significant prognostic factors for disease recurrence-free survival (DFS) and cause-specific survival (CSS). Age is a very important prognostic factor. Young age affects only DFS, whereas old age is related to both DFS and CSS. Aggressive variants, such as tall cell and hobnail variants, high Ki-67 labeling index, and TERT promoter gene mutations, are pathological and molecular prognostic factors. FTC is generally diagnosed based on postoperative pathology. Old age and large tumor size are associated with poor prognosis. Importantly, FTC is classified as minimally invasive, encapsulated angioinvasive, and widely invasive, which are closely related to the prognosis. Recent studies have demonstrated that the grade of vascular invasion is an important prognostic factor, whereas capsular invasion is not, because widely invasive FTC with no vascular invasion has an excellent prognosis. Dynamic markers, such as thyroglobulin doubling rate, metastatic tumor volume-doubling rate, and immunological indicators, such as the neutrophil-to-lymphocyte ratio, are useful for predicting the prognosis and evaluating the effectiveness of treatments, such as radioactive iodine therapy and molecular targeted therapy for recurrent lesions. Clinicians should accurately evaluate the prognostic markers of PTC and FTC in the pre-, intra-, and postoperative phases.