[Uveal metastasis of thyroid carcinomas. About 3 cases]

Orbital Radioiodine Uptake in Epithelial Conjunctival Inclusion Cyst on Scintigraphy in a Patient With Differentiated Thyroid Cancer

ABSTRACT

Abnormal focal accumulation of 131I is generally a reliable indicator of differentiated thyroid cancer metastases. However, many examples of false-positive 131I uptake were reported but only a few with orbital accumulation of radioiodine. We report the case of a 68-year-old woman with differentiated thyroid cancer who underwent thyroid remnants ablation with radioiodine. A focus of considerable 131I uptake corresponding to a small, periorbital tumor was detected on posttherapy whole-body 131I scan and head SPECT/CT. The tumor was surgically removed, and pathology revealed a conjunctival inclusion cyst with no features of thyroid tissue. Orbital 131I uptake was not detected on follow-up scans.

Orbital Radioiodine Uptake on Scintigraphy in a Patient with Thyroid Cancer

BACKGROUND

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.

CASE REPORT

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.

DISCUSSION

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.