Unilateral Proptosis Due to Orbital Metastasis as a Presenting Clinical Manifestation of Carcinoma of the Thyroid

Differentiated thyroid cancers commonly present with thyroid swelling with or without regional nodal involvement and usually have an indolent clinical course. We report a rare case of unilateral proptosis due to orbital metastasis as a primary manifestation of differentiated thyroid carcinoma. A 55-year-old woman presented with protrusion of the left eye for 6 months and progressively diminishing vision for 7 days duration. She had an anterolateral orbitotomy with radical excision of the tumor that had shown enhancement with osteolytic destruction on contrast-enhanced CT scan. Histopathological examination of the orbital mass revealed a metastatic follicular carcinoma of the thyroid. She then had a total thyroidectomy with lymph node dissection, final histopathology of which revealed widely invasive follicular carcinoma of the thyroid. A diagnostic radioiodine scan after thyroid hormone withdrawal showed residual tumor in the thyroid bed, left orbital, and multiple bony metastases for which she underwent high-dose radioiodine therapy.The case is important due to its unusual clinical presentation that was also the primary manifestation. Even though orbital metastasis of carcinoma of the thyroid is rare, thyroid carcinoma should be considered as a potential primary tumor in such presentations.