Variants and pitfalls on radioiodine scans in pediatric patients with differentiated thyroid carcinoma.

Abstract

Potentially false-positive findings on radioiodine scans in children with differentiated thyroid carcinoma can mimic functioning thyroid tissue and functioning thyroid carcinomatous tissue. Such false-positive findings comprise variants and pitfalls that can vary slightly in children as compared with adults. To determine the patterns and frequency of these potential false-positive findings on radioiodine scans in children with differentiated thyroid carcinoma. We reviewed a total of 223 radioiodine scans from 53 pediatric patients (mean age 13.3years, 37 girls) with differentiated thyroid carcinoma. Focal or regional activity that likely did not represent functioning thyroid tissue or functioning thyroid carcinomatous tissue were categorized as variants or pitfalls. The final diagnosis was confirmed by reviewing the concurrent and follow-up clinical data, correlative ultrasonography, CT scanning, serum thyroglobulin and antithyroglobulin antibody levels. We calculated the frequency of these variants and pitfalls from diagnostic and post-therapy radioiodine scans. The most common variant on the radioiodine scans was the thymic activity (24/223, 10.8%) followed by the cardiac activity (8/223, 3.6%). Salivary contamination and star artifact, caused by prominent thyroid remnant, were the most important observed pitfalls. Variants and pitfalls that mimic functioning thyroid tissue or functioning thyroid carcinomatous tissue on radioiodine scan in children with differentiated thyroid carcinoma are not infrequent, but they decrease in frequency on successive radioiodine scans. Potential false-positive findings can be minimized with proper knowledge of the common variants and pitfalls in children and correlation with clinical, laboratory and imaging data.