Orbital Radioiodine Uptake on Scintigraphy in a Patient with Thyroid Cancer

Orbital radioiodine uptake in patients with thyroid cancer is very uncommon with only a few reported cases, most of them being metastasis. The accumulation of ¹³¹I in nonthyroidal tissues and body fluids can lead to false-positive results in scintigraphy, which are sometimes difficult to differentiate from true metastases.

A post-therapy ¹³¹I whole-body (WBI) scintigraphy in an asymptomatic 57-year-old female with papillary thyroid carcinoma (PTC) previously treated with total thyroidectomy and 6 ablative radioiodine doses showed a focal uptake in the right eyeball region. The lesion, placed in the orbital space, was surgically removed, and histology revealed a conjunctival inclusion cyst.

Ocular and orbital metastases from thyroid cancer, as well as some non-neoplastic disorders or contamination, are possible causes for ¹³¹I uptake in the orbital region in scintigraphy. Conjunctival inclusion cyst is a condition associated with incidental ¹³¹I uptake that had not been reported before and should be ruled out as a non-metastatic cause of orbital radioiodine uptake in patients with PTC.