Localization and identification of parapharyngeal metastases from differentiated thyroid carcinoma by 131I-SPECT/CT

Background Parapharyngeal metastasis is a rare event in differentiated thyroid carcinoma (DTC). The 131I-single photon emission CT (SPECT)/CT allows better localization and definition for metastases in DTC. The aim of this study was to assess the value of 131I-SPECT/CT for the diagnosis of parapharyngeal metastasis in patients with DTC. Methods Consecutive patients with DTC (n = 561) treated with 131I for the ablation of remnant or treatment of metastases were enrolled. A 131I-SPECT/CT was performed when there were abnormal findings indicative of parapharyngeal metastasis on 131I-whole-body scan (WBS). Results A total of 15 lesions were found to be parapharyngeal metastasis in 14 of 561 patients with DTC after the use of 131I-SPECT/CT. The incidence rate of parapharyngeal metastasis was about 2.5% in DTC. Of the 15 lesions, only 5 lesions were CT-positive. The remaining 10 lesions were either ignored or indeterminate by the CT alone. Conclusion The 131I-SPECT/CT can identify parapharyngeal metastasis at an early stage. Parapharyngeal metastasis in DTC is relatively frequent after the use of 131I-SPECT/CT. © 2010 Wiley Periodicals, Inc. Head Neck, 2011