Orbital metastasis from papillary thyroid carcinoma (PTC) is an exceptionally rare clinical manifestation and is often overlooked in differential diagnoses, especially in patients with advanced, radioiodine-refractory disease. Distant metastases from PTC commonly involve the lungs and bones, while orbital involvement is extremely uncommon and can lead to serious visual symptoms and functional impairment. Herein, we present the case of a 51-year-old male who was initially diagnosed with PTC in 2014 and treated with total thyroidectomy and radioactive iodine (RAI) therapy. Over the following years, the patient developed extensive pulmonary and mediastinal lymph node metastases that showed poor response to repeated RAI administration. He subsequently underwent external beam radiation therapy (EBRT) for local control of mediastinal disease.
Eighteen months later, the patient presented with new-onset diplopia, blurred vision, and swelling in the left eye. A brain MRI revealed a mass measuring 39×33 mm in the posterolateral wall of the left orbit, which was applying pressure on the optic nerve and surrounding structures. A biopsy, along with immunohistochemistry, confirmed the lesion was of thyroid origin. Given the stability of the patient's pulmonary disease and good performance status, the patient received radical EBRT to the orbital lesion (60 Gy in 30 fractions), which led to significant symptomatic improvement and tumor shrinkage on follow-up imaging.
This case underscores the importance of considering rare metastatic patterns in advanced PTC, particularly when patients present with new focal symptoms. It also demonstrates the effectiveness of EBRT as a local control strategy in iodine-refractory metastatic thyroid cancer, offering symptom relief and delaying the need for systemic therapy.