| Abstract: |
The thyroid contains two endocrine cell types: follicular cells, which secrete thyroid hormones, and parafollicular or C cells, the primary source of calcitonin. Most of this chapter is dedicated to reviewing the molecular and phenotypic characteristics of cancers derived from follicular cells, as they represent about 95% of all cancers arising from this gland, focusing in particular on oncoproteins that represent potential therapeutic targets for the disease. The oncogenic repertoire of thyroid cancers of follicular cells There are two major histological types of differentiated thyroid cancer: papillary (PTC) and follicular (FTC; Figure 64.1). PTCs arise as sporadic tumors, with a female preponderance, and are the most common form of the disease. Several key genetic events involved in PTC pathogenesis have been identified. Mutations of the receptor tyrosine kinases (RTK) RET or TRK, of the three RAS genes (NRAS>HRAS>KRAS), or of BRAF account for about 70% of these tumors. With very rare exceptions mutations in these genes is mutually exclusive in thyroid carcinomas of all stages of differentiation, suggesting that just one activating event in the RTK-Ras-Raf-MEK-ERK pathway is sufficient to drive tumorigenesis (1). © Cambridge University Press 2014. |
