The Thyroid Gland

Ultrasound (US) followed by USG-FNA is paramount for the evaluation of thyroid nodules. This chapter covers the US of normal thyroid gland, thyroid gland anomalies, and thyroid nodules including US features that prompt FNA cytology correlation. USG-FNA techniques for sampling thyroid nodules and specimen handling are also included. The FNA cytology diagnosis of benign, atypical, and malignant conditions described is based on The Bethesda System for Reporting Thyroid Cytopathology 2023 nomenclature. Cytologic features, molecular profile, immunocytochemistry, and US features of the various entities are described. Cytologic entities are correlated with histopathology following the 2022 WHO classification of thyroid tumors. A condensed review of molecular classification and profiles of thyroid tumors is provided with emphasis on the ancillary tests used in atypical lesions of undetermined significance and their therapeutic implications are also described at the end of this chapter. Numerous cytology, US figures, and video clips complement the text.