Our series was composed by 255 thyroid samples from 229 patients. Cases were collected from the files of the Institute of Molecular Pathology and Immunology of the University of Porto (IPATIMUP, Porto, Portugal), corresponding to patients with thyroid tumors (n = 229) operated and followed in two university hospitals. Samples from normal thyroid (n = 25) and Graves’ disease (n = 1) were obtained from the contralateral lobe of the surgical specimens. Carcinomas series was composed by 193 PTCs (123 cases of classical PTC (cPTC), 47 cases of follicular variant of PTC (fvPTC) and 23 cases of other PTC variants), 23 follicular thyroid carcinomas (FTC) and 13 poorly differentiated thyroid carcinomas (PDTC). In 166 of the cases, there was only formalin-fixed paraffin-embedded (FFPE) representative tissue; in 45 cases, there were FFPE samples and correspondent frozen tissue (the tumors were divided at the time of surgery) and in 18 cases, there was only frozen tissue available. Frozen material was collected at the time of surgery and conserved at −80°C. The histology of all tumor samples was reviewed by three pathologists (CE, ER, MSS) according to the criteria of the World Health Organization (31). Clinicopathological and molecular data of the 229 patients with carcinoma are summarized in Supplementary Table 1 (see section on supplementary data given at the end of this article). In 141 cases, follow-up data were available. The number of 131I treatments varied from 1 to 5 treatments (mean 1.9), and the cumulative total dose of RAI was between 30 and 1146 mCi (mean 251 mCi). This work was approved by the Ethic Committee for Health (CES) of the Hospital Center of São João (CHSJ)/Faculty of Medicine of the University of Porto (FMUP) (CES 137 284–13) and by the Ethic Committee of the Faculty of Medicine of the University of Coimbra (n° 1309). All the procedures described in this study were in accordance with national ethical standards (Law n° 12/2005) and Helsinki declaration. Patients signed an informed consent form.