Figure 5. Figures 5, 6. (5) Thyroglossal duct cyst in a 39-year-old man. Contrast-enhanced CT scan shows a hypoattenuated mass (m) in the right strap muscles. (Courtesy of the Department of Radiology, Neuroradiology Section, University of California at San Francisco.) (6) Thyroglossal duct cyst in a 71-year-old man with a 1-year history of progressive swelling on the left side of the neck. (a) Contrast-enhanced CT scan shows a large cystic mass arising from the left strap muscles. (b) Photograph of the cut specimen shows the smooth inner lining and roughened exterior surface of the cyst.