SUN-330 Unmasking Aggression: A Case Report on Micropapillary Thyroid Cancer with Orbital, Nasopharyngeal Cavity, Vertebral Metastases

Abstract Disclosure: D.L. Elazegui: None. M.D. Capellan: None. A 41-year-old female with an unremarkable medical history presented with diplopia, which began three years prior to her initial consultation. She reported diplopia and blurred vision without accompanying symptoms. Imaging revealed a clival mass, and the patient opted for serial monitoring. Over time, she developed exertional dyspnea and dysphagia. Subsequent imaging showed enlargement of the clival mass with extension into the nasopharyngeal cavity. The mass was found to completely obstruct the nasopharyngeal airways and internal carotid arteries, with evidence of intracranial metastases. A biopsy of the clival mass confirmed metastatic carcinoma originating from a thyroid primary, supported by immunohistochemical staining: Pancytokeratin positive, TTF-1 positive, PAX8 positive. Thyroid histopathology identified papillary thyroid carcinoma, follicular subtype. The patient underwent total thyroidectomy, with histopathology confirming micropapillary thyroid carcinoma. Postoperatively, in preparation for radioactive iodine ablation therapy, the patient experienced worsening vision and hearing loss. Imaging indicated further growth of the lobulated mass involving the nasopharynx, nasal cavity, bilateral ethmoid and sphenoid sinuses, with associated lytic osseous changes, airway obstruction, and vascular encasement. The metastatic lesions exhibited more aggressive behavior than the primary thyroid carcinoma. The treatment plan includes external beam radiation therapy to target orbital, nasopharyngeal, and vertebral metastases, followed by radioactive iodine therapy and potential tyrosine kinase inhibitor therapy to delay disease progression. Reports of distant metastases from micropapillary carcinoma are rare. Studies have identified risk factors such as tumor diameter, advanced age, lymph node metastasis at diagnosis, and the follicular variant. External beam radiotherapy is integral to managing thyroid cancer with distant metastases, enhancing local control and reducing relapse risk, especially in cases of gross extrathyroidal extension or inoperable disease. In this case, symptom control was prioritized due to airway obstruction, necessitating initial radiotherapy. A personalized management approach is crucial in this rare presentation of an indolent cancer with distant metastases. The endocrinologist should focus on symptom control, palliative care, and subsequent radioactive iodine ablation therapy. Presentation: Sunday, July 13, 2025