The Thyroid Gland

Abstract

Cytology is a widely used, safe, and reliable investigation for thyroid nodules, providing not only distinction of benign from malignant lesions but also a specific diagnosis of the type of malignancy in the majority of cases. A major aim of cytological diagnosis is to reduce unnecessary surgery. The accuracy of cytological diagnosis can be improved further by ancillary techniques such as immunohistochemistry, and there is a growing prospect of molecular testing for known genetic abnormalities. In recent years, there have been attempts to unify the diagnostic approach to thyroid cytology and improve accuracy by promoting the use of diagnostic categories, and several reporting systems have been introduced, such as the Bethesda system for thyroid cytology reporting and more recently a guideline document introduced by the Royal College of Pathologists of the UK. In this chapter, the approach to cytological diagnosis of common thyroid lesions is described.