General Considerations of Thyroid Cancer and Classification
18 April 2018 (online)
Thyroid cancer is the most common malignant disease in endocrine system and is rapidly increasing in incidence.
The increasing incidence partially reflects earlier detection of small asymptomatic cancers because of prevalence of screening. However, the incidence has also increased across all tumor sizes and stages. Most of thyroid cancers show biologically indolent phenotype and have an excellent prognosis with survival rates of more than 95% at 20 years although the recurrence or persistent rate is still high. The incidence of thyroid cancer is about three to four times higher among females than males worldwide, ranking the sixth most common malignancy diagnosed in women.
Most primary thyroid cancers are epithelial tumours that originate from thyroid follicular cells. These cancers develop three main pathological types of carcinomas: papillary thyroid carcinoma (PTC), follicular thyroid carcinoma (FTC) and anaplastic thyroid carcinoma (ATC).
Thyroid cancer can occur at any age but it is rare in childhood. Most tumors are diagnosed during third to sixth decade of life. The general pathological classifications and clinical features of follicular cell derived thyroid carcinomas are overviewed, and recent advances of genetic alterations are discussed in this review.