In this radiology lecture, we review the ultrasound appearance of thyroglossal duct cyst with two unique cases! Key teaching points include: * Thyroglossal duct cyst is the most common congenital neck cyst. * Most present before age 18 as a midline, fluctuant neck mass near hyoid bone. * Often asymptomatic unless superinfected = Abscess, draining sinus. * Epithelial-lined cysts caused by failure of normal involution of thyroglossal duct. * Can occur anywhere from foramen cecum of tongue to thyroid gland. * Most are infrahyoid, followed by hyoid and suprahyoid. * Most are midline, but can be paramedian (more likely if infrahyoid). * If infrahyoid, typically embedded in strap muscles. * May move with swallowing and elevates with tongue protrusion. * Presence of normal thyroid gland should be confirmed. * When simple, typically appears as an anechoic midline neck mass near hyoid bone. * Cyst complexity usually due to superinfection: Proteinaceous internal debris and septations, thick irregular walls, increased blood flow and surrounding inflammation. * Solid components may indicate ectopic thyroid or rarely (less than 1% of cases) thyroid cancer (typically papillary subtype). * Tx: Resection of cyst, surrounding tissue along the thyroglossal tract, and midline portion of hyoid bone = Sistrunk procedure. To learn more about the Samsung RS85 Prestige ultrasound system, please visit: https://www.bostonimaging.com/rs85-prestige-ultrasound-system-4 Click the YouTube Community tab or follow on social media for bonus teaching material posted throughout the week! Instagram: https://www.instagram.com/radiologistHQ/ Facebook: https://www.facebook.com/radiologistHeadQuarters/ Twitter: https://twitter.com/radiologistHQ Reddit: https://www.reddit.com/user/radiologistHQ/