False-positive ¹³¹I Uptake in a Carotid Body Tumor Mimicking Nodal Metastasis in Differentiated Thyroid Carcinoma: Implications of Hybrid SPECT/CT.

Carotid body tumors (CBTs) are uncommon neuroendocrine neoplasms which typically demonstrate avidity on somatostatin receptor-based imaging rather than radioiodine studies. We report a 50-year-old woman with follicular variant papillary thyroid carcinoma who, eight years post-treatment, developed a CBT incidentally demonstrating mild radioiodine uptake. SPECT/CT localized this unexpected uptake to the CBT, representing a rare false-positive finding. This case underscores the importance of correlating functional imaging with structural imaging to avoid misinterpretation of nonspecific radioiodine uptake as metastatic disease and prevent unnecessary therapeutic interventions.