Persistent 131I uptake in the thyroglossal duct after thyroid ablation: A case report and literature review

Rationale: Persistent midline radioiodine uptake after thyroid remnant ablation can mimic metastatic disease and lead to unnecessary re-treatment. We report a case of persistent iodine-131 ( 131 I) uptake in the thyroglossal duct region with undetectable thyroglobulin (Tg). Patient concerns: A 45-year-old woman was found to have thyroid nodules on routine ultrasound, and further evaluation supported papillary thyroid carcinoma. Diagnoses: After total thyroidectomy and central neck dissection, post-ablation and follow-up 131 I imaging demonstrated persistent focal uptake in the midline neck. Single photon emission computed tomography, computed tomography (SPECT/CT) localized the activity to the thyroglossal duct tract, while repeated serum Tg remained undetectable and no structural lesion was identified, supporting a benign thyroglossal duct remnant. Interventions: The patient underwent total thyroidectomy with central neck dissection, followed by 100 mCi 131 I remnant ablation after thyroid hormone withdrawal. She then received levothyroxine for thyroid-stimulating hormone suppression. Six months later, levothyroxine was withdrawn again for 4 weeks, and a low-dose diagnostic 131 I scan (3 mCi) with SPECT/CT was performed. Outcomes: Diagnostic 131 I imaging at 6 months again demonstrated persistent uptake at the same thyroglossal duct site, with no uptake in the thyroid bed, undetectable Tg, and no structural evidence of recurrent disease. The patient was managed conservatively with thyroid-stimulating hormone suppression and periodic biochemical and ultrasound follow-up. Lessons: For isolated midline 131 I uptake after ablation, SPECT/CT localization along the thyroglossal duct tract combined with undetectable Tg supports a benign thyroglossal duct remnant and favors observation with structured follow-up over empiric repeat ablation.