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

Abstract

Abnormal focal accumulation of 131 I is generally a reliable indicator of differentiated thyroid cancer metastases. However, many examples of false-positive 131 I 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 131 I uptake corresponding to a small, periorbital tumor was detected on posttherapy whole-body 131 I scan and head SPECT/CT. The tumor was surgically removed, and pathology revealed a conjunctival inclusion cyst with no features of thyroid tissue. Orbital 131 I uptake was not detected on follow-up scans.

Concurrent Benign Iodine-Avid Thymic and Liver Cysts Mimicking Metastatic Disease on 131I Whole-Body Scintigraphy

“…After 6 years of clinic follow-up, the serum Tg remains <1.0 μg/L, and she remains asymptomatic and free of disease recurrence. 131 I accumulation in cysts has been reported in the literature involving many sites such as epithelial conjunctival inclusion cyst, 1 epidermal cyst, 2 thymus, 3–6 thyroglossal duct, 5 bronchogenic cyst, 4,5,7,8 breast, 5,7 liver, 4,5 hepatic hydatid cyst, 7 renal, 4,5,7,9 ovary, 4,5,9 bone, 9 uterine menstruation dermoid cyst, 9 pleuropericardial, 4,5 sebaceous cyst, 4,5,7 nasolacrimal duct, 4,5 laryngeal cyst, 4 gastrointestinal duplication cyst, 4 nabothian cyst, 4,10 and pancreatic lymphoepithelial cyst 11 . The postulated mechanism of 131 I uptake in the cysts varies and includes incomplete active transport or passive diffusion of the chemical materials and 131 I between the cyst and adjacent tissue followed by its retention within the cystic structure, 5,10–12 chronic inflammation resulting in hypervascularity and increased capillary permeability, 13,14 expression of sodium-iodide symporter in the cystic epithelial cells, 13,15 and organification of 131 I in leukocytes 14 .…”