When a Thyroid Nodule is Actually an Unusual Intrathyroidal Thyroglossal Duct Cyst: Case Report

Aims and background: Thyroglossal duct cysts (TDCs) typically present as midline neck masses located below the hyoid bone.Intrathyroidal thyroglossal duct cysts (ITTDCs), however, are exceedingly rare.This report outlines an uncommon case of ITTDC to emphasize the importance of differential diagnosis and appropriate surgical management.Case description: A 36-year-old woman underwent an ultrasound examination that revealed a cystic lesion within the left lobe of the thyroid, initially interpreted as a thyroid nodule.A left lobectomy with isthmectomy was performed.Histopathological analysis postoperatively identified the lesion as an ITTDC.Conclusion: Although extremely rare, ITTDCs can mimic benign thyroid nodules and cysts.Recognition of this entity is crucial, especially since surgical management may require a combination of thyroidectomy and the Sistrunk procedure to prevent recurrence.Clinical significance: Because intrathyroidal localization of TDCs is so uncommon, they are seldom considered in differential diagnoses of thyroid lesions.However, accurate identification is important due to the unique surgical approach required.In the absence of thyroglossal duct remnants or external tract involvement, excision without the Sistrunk procedure may suffice, as demonstrated in this case, where no recurrence was observed over a 5-year follow-up.Nonetheless, the Sistrunk procedure remains the standard of care for typical TDCs.