The CT and MR imaging features of carcinoma arising in thyroglossal duct remnants.

C M Glastonbury, H C Davidson, J R Haller, H R Harnsberger

Carcinoma arising in thyroglossal duct remnants is a well-described entity in the pathology and surgery literature, but it has little recognition in the radiology literature. Preoperative diagnosis may alter surgical management, although this diagnosis is rarely made. This study was undertaken to determine the radiologic features that might differentiate carcinoma from benign thyroglossal duct cysts. Twenty-one cases of nonpediatric thyroglossal duct anomalies imaged at our institution during a 15-year period were reviewed retrospectively. The images were assessed for lesion wall thickness, enhancement, soft-tissue component, calcification, and loculation of the cystic component. Three additional cases of thyroglossal duct carcinoma obtained from outside institutions were reviewed for these features also. Six cases of thyroglossal duct carcinoma were reviewed. All cases of carcinoma had solid soft-tissue elements visible on CT scans or MR images, compared with three of 18 cases of benign thyroglossal duct cysts. The malignant component was seen as a small peripherally based mass in relation to a cyst, a solid mass in the expected course of the thyroglossal duct, or a complex invasive mass also in the midline of the neck. CT only revealed calcification in cases of carcinoma, within either the primary carcinoma mass or a metastatic node. Thyroglossal duct carcinoma should be suspected in an adult patient in the presence of a solid nodule or invasive features in association with a thyroglossal duct lesion visible on CT scans or MR images. The presence of calcification, which is seen best on CT scans, may be a specific marker for carcinoma.