Noninvasive Follicular Thyroid Neoplasm With Papillary-Like Nuclear Features Arising in the Thyroglossal Duct: A Case Report and Literature Review.

A noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) is a recently reclassified thyroid tumor characterized by low malignant potential and typically confined to the thyroid gland. Its occurrence in a thyroglossal duct remnant is exceedingly rare, with only a few cases reported. Herein, we describe the case of a 74-year-old man who presented with a painless, progressively enlarging midline anterior neck mass. Ultrasonography and contrast-enhanced computed tomography demonstrated a well-circumscribed cystic lesion along the thyroglossal duct tract. Fine-needle aspiration cytology revealed a follicular-patterned lesion, consistent with Bethesda category IV. The patient subsequently underwent surgical excision via the Sistrunk procedure. Histopathological examination showed a completely encapsulated follicular lesion with papillary-like nuclear features, without true papillae, capsular, or vascular invasion, thereby confirming the diagnosis of NIFTP arising in ectopic thyroid tissue. Given the absence of invasive features, no additional therapy was required, and no recurrence was observed at the six-month follow-up. This case highlights the diagnostic limitations of preoperative cytology in ectopic thyroid lesions and underscores the importance of complete surgical excision when malignancy cannot be definitively excluded.