A rare metastatic follicular thyroid carcinoma masquerading as primary sinonasal carcinoma presentation with unusual orbit, skull base and brain metastases

Abstract

Tumour involving the sinonasal tract account for only 1% of all malignancies. The large majority of tumours affecting sinonasal tract are mainly primary neoplasm or from direct extension of adjacent region; metastatic tumour affecting sinonasal tract are extremely rare. Most of the metastases are originate from carcinoma inferior to the clavicle, including renal, breast, lung, and prostate. The incidence of metastases to sphenoid sinus are even rare. We describe a rare case of metastases of FTC to sinonasal tract, mimicking primary sinonasal carcinoma presentation, with unusual orbit, skull base and brain metastases. A 66-year-old lady with history of subtotal thyroidectomy for FTC presented with epistaxis associated with proptosis of left eye. Nasal endoscopy revealed vascularised mass occupying the entire left nasal cavity. Endoscopic transnasal biopsy was performed which showed metastatic FTC with positive immunochemical staining for thyroglobulin, and thyroid transcription factor-1. Computed tomography angiography demostrated a large vascular tumour involving the left maxillary sinus, bilateral ethmoid and sphenoid sinuses. The mass causing erosion of nasal septum and pterygoid plates and left temporal bone, with extension to left orbit, infratemporal fossa and intracranial. Patient received thyroid stimulating hormone suppression therapy followed by radio-iodine ablation. As surprisingly rare, the purpose of our study is to raise the awareness regarding the possibility of FTC metastatizing to sinonasal tract, orbit, skull base and intracranial. The completion thyroidectomy intervention is crucial for better future prognosis. Thyroid carcinoma should be considered in differential diagnosis of epistaxis and potential primary neoplasm in patient with orbital metastases.