Unilateral proptosis with thyrotoxicosis resulting from solitary retroorbital soft tissue metastasis from follicular carcinoma thyroid.

Unilateral proptosis can be of neoplastic origin, even if the results of thyroid function tests suggest hyperthyroid disease, and it needs proper investigation with a computed tomographic scan of the orbit. The authors present a case of left-sided proptosis resulting from a metastasis in the retroorbital soft tissue from follicular carcinoma of the thyroid. A nodular goiter involving the left lobe and isthmus was found. The initial thyroid function test values suggested hyperthyroid disease and the patient had clinical signs of toxicity. A computed tomographic scan of the orbit revealed a left-sided retroorbital soft tissue mass, part of which was resected and found be to a metastasis from follicular carcinoma of thyroid. Total thyroidectomy was performed and the patient was treated with I-131 after operation. The proptosis resolved with I-131 treatment.