Thyroid Ultrasound > Top 10 Pathology > 1. Cysts and Anatomic Variants


Cysts and Anatomic Variants

Cysts may be colloid (hyperplastic or adenomatous), simple or hemorrhagic in nature. On sonography, cystic areas may contain either serous fluid or colloid; old hemorrhage and resultant echogenic fluid may also be noted. Punctuate highly echogenic foci with ring-down artifact (see below image from Ultrasound Clinics Apr 2009) represent colloid crystals within colloid cysts. If residual strands of thyroid tissue remain within the cystic areas, a characteristic honeycomb appearance may result. Nonuniform patterns of degeneration may produce mural nodules, septations, or internal debris. 

Normal variants of the thyroid diverticulum are represented by a pyramidal lobe of thyroid gland and/or a ligament (thyroglossal) extending superiorly from either a pyramidal lobe (if it exists) or the thyroid isthmus up to the hyoid bone. The foramen cecum of the tongue is a normal marker of the site of the thyroid diverticulum. A minority of patients have a thin pyramidal lobe (see CT image below) extending superiorly from the isthmus that can be seen in childhood and in conditions that cause generalized enlargement of the thyroid.

Thyroglossal (Duct) Cyst: This is the most common anomaly of the head and neck. It is a cyst located beneath the skin of the anterior midline of the neck, usually just below the hyoid bone. It is the second most common cause of a neck mass in children (the most common being lymphadenopathy). A very helpful clue in diagnosing thyroglossal cysts is that they move superiorly when the child protrudes his/her tongue. If an infected cyst ruptures through the skin to drain, it is called a thyroglossal sinus. Sonographically, contain low-level intraluminal reflectors, presumably due to bleeding or infection.

Lingual Thyroid: Thyroid tissue may sometimes be left behind embedded in the tongue, most commonly seen in a midline suprahyoid position between the foramen cecum of the tongue and the epiglottis, which occurs 1 in 100,000 healthy individuals. This is usually asymptomatic. However, if the mass becomes large, symptoms of dysphagia (difficulty swallowing), dysphonia (difficulty speaking), or dyspnea (difficulty breathing) may arise. The majority of persons with symptomatic lingual thyroid tissue have no thyroid gland in the neck. The way to determine if a suspicious mass in the tongue is composed of thyroid tissue is to see if it takes up administered I123.