Enlargement and Transformation of Thyroglossal Duct Cysts in Response to Radiotherapy: Imaging Findings

A 54-year-old man before and after IMRT for treatment of a T2N2B base of tongue squamous cell carcinoma. A, Sagittal reconstructed image of a contrast-enhanced CT series before RT showing an isodense structure coursing from a location posterior to the hyoid, anteroinferiorly through the thyrohyoid membrane, and finally into a position anterior to the thyroid cartilage (arrows). B, Sagittal reconstructed image obtained 30 days after the completion of RT. The lesion is clearly larger and more cystlike (arrows). C, Axial, contrast-enhanced CT image obtained 7 months after the image in 2B, during an asymptomatic period. The cyst appeared more complex and irregular, with suspected inflammatory changes peripherally and in the nearby platysma muscles. Infection was suggested. Results of an ultrasound-guided biopsy revealed a benign cyst. It was finally hypothesized that self-massage for the purpose of improving lymphatic drainage and alleviating edema caused irritation of the cyst and the adjacent soft tissues. D, Axial, contrast-enhanced CT image obtained 90 weeks after RT. Inflammatory changes had long since resolved, and the cyst is both smaller and less conspicuous, as was generally the case with our series of cases.