Diagnosis: Papillary carcinoma in a thyroglossal duct cyst (TGDC)
Embryologically, the thyroid gland forms along the base of the tongue during the third week of gestation and subsequently descends in the neck to its final pretracheal location along an epithelial tract, the thyroglossal duct. Normally, the thyroglossal duct involutes completely between the eighth and tenth weeks of gestation.1 However, persistent secretory epithelial tissue can lead to a TGDC, the most common congenital mass in the anterior aspect of the neck. The TGDC generally occurs in the midline, or just off the midline, and typically presents in pediatric patients. The classic TGDC will be located at or below the hyoid bone,2 while approximately 20% of TGDCs will occur in a suprahyoid location. Radiologically, TGDCs appear on ultrasonograms, CTs, or magnetic resonance images (MRIs) as relatively simple, well-circumscribed cystic lesions that are intimately associated with the hyoid bone and anterior strap muscles. Superimposed infection, trauma, or intervention may lead to a more complex, thick-walled, and nodular appearance.