The number of thyroid cancers is increasing. Standard treatment usually includes primary surgery, thyroid-stimulating hormone suppressive therapy, and ablation of the thyroid remnant with radioactive iodine (RAI). Despite the generally good prognosis of thyroid carcinoma, about 5% of patients will develop metastatic disease, which fails to respond to RAI, exhibiting a more aggressive behavior. The lack of specific, effective and well-tolerated drugs, the scarcity of data about the association of multi-targeting drugs, and the limited role of radioiodine for dedifferentiated thyroid cancer, call for further efforts in the field of new drugs development. Rearranged during transfection (RET)/papillary thyroid carcinoma gene rearrangements, BRAF (B-RAF proto-oncogene, serine/threonine kinase) gene mutations, RAS (rat sarcoma) mutations, and vascular endothelial growth factor receptor 2 angiogenesis pathways are some of the known pathways playing a crucial role in the development of thyroid cancer. Targeted novel compounds have been demonstrated to induce clinical responses and stabilization of disease. Sorafenib has been approved for differentiated thyroid cancer refractory to RAI.

The most common thyroid malignancy is papillary thyroid cancer (PTC). Mortality rates from PTC mainly depend on its aggressiveness. Geno- and phenotyping of aggressive PTC has advanced our understanding of treatment failures and of potential future therapies. Unraveling molecular signaling pathways of PTC including its aggressive forms will hopefully pave the road to reduce mortality but also morbidity from this cancer. The mitogen-activated protein kinase and the phosphatidylinositol 3-kinase signaling pathway as well as the family of RAS oncogenes and BRAF as a member of the RAF protein family and the aberrant expression of microRNAs miR-221, miR-222, and miR-146b all play major roles in tumor initiation and progression of aggressive PTC. Small molecule tyrosine kinase inhibitors targeting BRAFmediated events, vascular endothelial growth factor receptors, RET/PTC rearrangements, and other molecular targets, show promising results to improve treatment of radioiodine resistant, recurrent, and aggressive PTC.

Differentiated thyroid tumors (DTTs) are characterized by significant molecular variability in both spatial and temporal intra-tumoral heterogeneity (ITH), that could influence the therapeutic management. ITH phenomenon appears to have a relevant role in tumor growth, aggressive behavior and drug resistance. Accordingly, characteristics and consequences of ITH in DTTs should be better analyzed and understood in order to guide clinical practice, improving survival. Consequently, in the present review, we investigated morphological and molecular ITH of DTTs in benign, borderline neoplasms and in malignant entities, summarizing the most significant data. Molecular testing in DTTs documents a high risk for recurrence of cancer associated with BRAF^V600E, RET/PTC 1/3, ALK and NTRK fusions, while the intermediate risk may be related to BRAF^K601E, H/K/N RAS and PAX8/PPARγ. In addition, it may be suggested that tumor genotype is associated with peculiar phenotype.

Based on the knowledge that diagnostic fine needle biopsy of the thyroid (FNAB) results in a prompt increase in circulating thyroglobulin (Tg); we evaluated whether Tg is indeed the postulated antigen for circulating antibodies against thyroid hormones (THAb). Preliminarily, we verified that FNAB causes the release into the bloodstream of iodinated, heterologous, and thus potentially immunogenic, molecules of Tg. Of the initially enrolled 400 patients, 214 had a number of blood drawings sufficient to evaluate over time (before FNAB and 1-3 h, 3 days, 15 days, 30 days, 3 months, 6 months, and 12 months after FNAB) the following parameters: THAb of both IgM and IgG classes, Tg antibodies (TgAb; by a sensitive immunoradiometric assay), and Tg (in the 156 patients who were TgAb negative). We found the following. 1) Serum Tg most often peaks 1-3 h after FNAB (61 +/- 45% of the baseline level; mean +/- SD). 2) Only 7% of the initially TgAb-negative patients converted to positive, and only 12% of those initially positive had an increase in the levels of TgAb. 3) THAb were detected in 0 of 400 patients before FNAB, but were found in 9 of 214 (4.2%) after FNAB. This proportion is 2 orders of magnitude higher than that (149 of 369,000 or 0.04%) found in consecutive patients attending European thyroid clinics. Of the 9 cases, 6 had Hashimoto's thyroiditis (HT), 2 had euthyroid colloid goiter, and 1 had Hurthle cell carcinoma. In the 5 of 9 cases who were TgAb negative, the post-FNAB increment in Tg was 21-99%, i.e. lower than that of the majority of patients (101-12,500%). 4) THAb were of the IgM class in all 9 (6 against T3 and 3 against T4), and were accompanied and/or followed up to 3 months after FNAB by IgG-THAb of the same specificity (2 against T3 and 1 against T4) in 3 cases. In a fourth case, IgM-T3 were followed by a long-lasting synthesis of IgG-T3 (i.e. up to 1 yr post-FNAB). All 4 cases with IgG-THAb had HT and remained TgAb positive. 5) In the 2 HT and the 3 non-HT patients with undetectable TgAb, THAb were of the IgM class only. 6) In the HT group, 2 risk factors for the development of post-FNAB THAb appeared to be pre-FNAB TgAb levels below 400 U/mL that did not increase after FNAB and Tg released from a colloid nodule. We conclude that Tg release from the thyroid is sufficient to elicit THAb synthesis. In patients with autoimmune thyroid disease (HT), this synthesis occurs with a frequency 10-fold higher than that in patients with nonautoimmune thyroid diseases (21% vs. 2%). However, in only a fraction of patients with autoimmune disease, who need to be TgAb positive by a sensitive assay, the primary immune response (IgM) is followed by a secondary one (IgG). As, once present, this secondary response is long lasting in only a minority of our patients, we think that this could contribute to the rarity of naturally occurring THAb.