The Parathyroid Gland

Ultrasound (US) evaluation of parathyroid glands is indicated for patients with primary, secondary, or tertiary hyperparathyroidism, and for patients with borderline or elevated serum calcium levels for localizing a parathyroid enlargement, tumor, or hyperplasia, particularly when the Sestamibi scan does not localize the affected parathyroid gland(s) before surgery. US is also indicated for evaluation of the concomitant presence or absence of thyroid nodule(s). Once the parathyroid and thyroid nodule(s) (if present) have been identified by US, an USG-FNA is performed for cytology and measurement of PTH levels in needle rinses. Surgical exploration will be the next step as clinically indicated. This chapter covers the cytology, US features, and molecular profiles of solid and cystic parathyroid tumors, including hyperplasia, adenoma, multiple glandular parathyroid adenomas, an atypical parathyroid tumor, parathyroid carcinoma, and parathyroid cysts. The histopathology of these tumors according to the 2022 World Health Organization classification of parathyroid tumors is highlighted. Video clips and numerous figures of cytologic and US features complement the text.