Neck rule 2 :Thyroglossal cyst

 

Key facts
The thyroglossal duct runs from the base of tongue at the foramen caecum to the thyroid gland.
The embryonic thyroid gland or thyroid anlage travels through the duct to reach its final normal position. Normally, the thyroglossal duct then involutes, but when the duct persists, a thyroglossal duct cyst can develop anywhere along this tract (figure).
The location is in the midline or paramedian.
65% are located infrahyoidal, 20% suprahyoidal and 15% at the level of the hyoid.
DDx: necrotic anterior cervical nodes and thrombosed jugular vein.

On the above image of a three-year old girl with a slowly enlarging tumor in the midline.
On ultrasound a hypo echoic ovoid smooth bordered lesion is seen at the level of the hyoid bone and slightly right off midline (left image).
During US examination, the lesion moves simultaneously with extrusion of the tongue.
Cystic nature and close relation to the hyoid bone makes thyroglossal duct cyst the most likely diagnosis.
Notice that a normal thyroid gland is present (right image).