The role of MR imaging in detecting nodal disease in thyroidectomy patients with rising thyroglobulin levels.

BACKGROUND AND PURPOSE One of the dilemmas facing clinicians treating patients with thyroid cancer is the evaluation of postthyroidectomy patients with rising serum thyroglobulin levels and indeterminate or normal findings on neck sonography. In this study, we examine the role of MR imaging in this subgroup of patients. MATERIALS AND METHODS We retrospectively reviewed MR images of patients with thyroid cancer with abnormal lymph nodes in the retropharyngeal and parapharyngeal spaces and determined the size and signal-intensity characteristics of these nodes. We reviewed patient charts for the following history: 1) thyroidectomy, 2) rising thyroglobulin levels, 3) iodine-131 radiation therapy, 4) neck dissection, and 5) pathology on neck sonography and chest CT. We reviewed pathology findings to determine if thyroid cancer metastases were present in these lymph nodes. RESULTS Eight patients had abnormal retropharyngeal space nodes, and 1 patient had a parapharyngeal space mass. Lymph nodes ranged from 7 to 25 mm. On MR imaging, 1 patient had a cystic node, 2 had complex nodes, and 6 had solid nodes. Eight patients had rising serum thyroglobulin levels and a history of thyroidectomy, radioiodine therapy, and neck dissection. Two of these patients had no pathologic nodes on sonography and normal findings on chest CT. Six patients had tissue sampling of their skull base node, and metastatic thyroid cancer was present in 5. CONCLUSIONS MR imaging of the neck should be considered in thyroidectomy patients with rising serum thyroglobulin levels and a history of radioiodine therapy and neck dissection. Radiologists should carefully examine the retropharyngeal and parapharyngeal spaces in these patients because nodal metastases may occur there more commonly than realized.