Current Knowledge in Thyroid Cancer—From Bench to Bedside

Thyroid cancer is the most common malignant endocrine tumour. Differentiated thyroid cancer (DTC) is a rare disease with increased incidence. In 2014, 62,980 (15,190 for males and 47,790 for women) cases of DTC were estimated in the US, compared to 2009 with 31,200 new cases [1]. In the US, estimated new cases for 2017 are 14,400 for males and 42,470 for females [2]. Thyroid cancer incidence rates are three-fold higher in women than in men (21 vs. 7 per 100,000 population), despite equivalent death rates (0.5 per 100,000 population) [2]. Worldwide data for thyroid cancer are available from GLOBOCAN 2012. The incidence of thyroid cancer in 2012 was estimated to be 298,102 new cases worldwide, representing 2.1% of all cancers [3]. Thyroid cancer types are classified according to their histological characteristics. DTC types comprise papillary thyroid cancer (PTC) and follicular thyroid cancer (FTC). DTC represents the majority of all thyroid carcinoma types with a generally positive prognosis [4]. The next group is anaplastic thyroid cancer (ATC), representing approximately 2% of all thyroid cancers. ATC is different from DTC, in that the cells mainly consist of undifferentiated cells with a very low or no similarity to normal thyroid tissue [5]. The one-year mortality rate is 90% [6]. Poorly differentiated thyroid cancer (PDTC) is similar to ATC; it is less common and has a poor prognosis [7]. Another thyroid cancer type is medullary thyroid cancer (MTC), deriving from neuroendocrine C-cells. The five-year survival rate is approximately 86% for MTC patients [8]. In recent years, studies in the field of thyroid cancer research have been performed in order to improve diagnosis with molecular biological techniques, to extend treatment strategies, to identify and verify thyroid specific biomarkers, as well as to identify cancer-specific changes in gene expression patterns and alterations of the protein content. Furthermore, new drugs, small molecules, and antibodies have been developed and tested in vitro and in vivo [9,10]. In clinical trials, the ratio between therapeutic and adverse effects was investigated [10]. Tyrosine kinase inhibitors (TKI) have become a new therapeutic option in patients with radioactive iodine (RAI)-refractory progressive DTC and in medullary thyroid cancer. In the last few years, new substances for targeted systemic therapy have been approved after their efficacy was demonstrated in Phase III trials. Most of them show a moderate response. However, adverse effects are common and have to be managed, such as hypertension, fatigue, diarrhoea, and others. In this Special Issue, a total of 16 excellent papers consisting of nine original research studies, six reviews, and one communication have been published, as detailed in Table 1. Several manuscripts focusing on the diagnosis [11–15], characterisation [16–19], and treatment [20–22] of thyroid cancer, as well as on alterations of thyroid cancer cells by altered gravity [23,24] or radiation damage of the thyroid gland [25], including genetics, proteomics, molecular, and cell biology, are published in this Special Issue. In addition, an original publication reports that the polymorphism