Risk and prognostic factors for differentiated thyroid cancer.

Papillary and follicular carcinomas, commonly referred to as follicular cell-derived differentiated thyroid carcinomas (DTC), account for 90% of all thyroid carcinomas. The prognosis of DTC is generally good, depending on the biologic behavior of the tumor and on the appropriate initial treatment which includes total thyroidectomy and ablation by radioiodine-131. However, a considerable number of patients, approximately 30%, as shown after 30 years of follow-up, have recurrent disease. It is thus of utmost importance to evaluate the prognostic factors, as derived from retrospective studies, and identify high risk patients. Age of more than 45 years or less than 25 years is a particularly strong independent prognostic factor; on the contrary gender is a poor prognostic factor. Histological type of the cancer especially tall cancer cells and columnar cancer cells, as well as increased vascular invasion of the tumor, lymph-node and distant metastases, are all considered as risk factors that can lead to poor prognosis. Combined prognostic factors have been used to form scoring systems (SS) such as AGES, MACIS, AMES, EORTC and TNM for a more precise description of high or low risk patients. However, prognostic significance of the SS is limited, since they do not take into consideration the clinical status or the treatment procedure during the course of the disease. Molecular factors such as rearrangements of genes RET/PTC, RAS mutations and fusion of, paired box and 8/peroxisome proliferator-activated receptor gamma (PAX8/PPARgamma) are also involved in thyroid cancer prognosis, while some others: human Pituitary- Tumor Transforming Gene (e.g. MIB-1, hPTTG) have been reported as additional prognostic factors. In this review we describe the risk and the prognostic factors of DTC as related to management and the outcome of DTC.