Metastatic Papillary Thyroid Carcinoma to the Nasal Cavity: When Niftp is Not Indolent

Background: Papillary thyroid carcinoma (PTC) is a well-differentiated malignancy with a favorable prognosis and rare distant metastases. The nasal cavity is an exceptionally uncommon site of metastasis. Non- Invasive Follicular Thyroid Neoplasm with Papillary-like Nuclear Features (NIFTP) is considered a low- risk thyroid lesion, and metastasis from such a lesion is exceedingly rare. Case Presentation: We report a case of a 58-year-old woman who presented with unilateral persistent epistaxis and anosmia, three years after undergoing thyroidectomy for a lesion diagnosed as NIFTP. Imaging revealed a hypervascular mass in the right nasal cavity with extension to the orbit and skull base. Biopsy and immunohistochemistry confirmed a metastatic papillary thyroid carcinoma. The patient underwent complete surgical excision via a combined endonasal and Rouge-Denker approach, followed by adjuvant radioactive iodine therapy. The postoperative course was uneventful. Discussion: This case highlights a rare metastatic presentation of PTC initially misclassified as NIFTP. The unusual site, delayed onset, and normal serum thyroglobulin levels contributed to the diagnostic challenge. It underscores the importance of accurate histopathological evaluation and vigilance in long-term follow-up. Conclusion: Sinonasal metastasis from PTC is extremely rare and can mimic primary nasal tumors. This case emphasizes the potential for misdiagnosis of NIFTP and the need for thorough pathological assessment and long-term monitoring.