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Iodine concentration by the thymus in thyroid carcinoma
F Vermiglio1, E Baudin, J P Travagli
1Department of Endocrinology, University of Messina, Italy.
Summary
Cystic Hassall's bodies in the thymus can trap radioactive iodine, mimicking thyroid cancer metastases. This finding explains misleading mediastinal radioiodine uptake in patients post-thyroidectomy.
Area of Science:
- Nuclear Medicine
- Endocrinology
- Pathology
Background:
- Papillary thyroid carcinoma treatment often involves radioactive iodine (131I) therapy and surveillance.
- Post-thyroidectomy patients may exhibit unexpected radioiodine uptake in non-thyroidal tissues.
- Accurate localization of radioiodine accumulation is crucial for effective cancer management.
Observation:
- A 14-year-old boy with papillary thyroid carcinoma showed mediastinal radioiodine uptake post-thyroidectomy.
- Imaging (CT, MRI) identified a mediastinal mass correlating with radioactivity.
- Surgical exploration revealed the thymus as the iodine-concentrating structure.
Findings:
- Histological examination of the thymus revealed cystic Hassall's bodies, not metastatic thyroid cancer.
- Secondary ion mass spectrometry confirmed iodine localization within these cystic Hassall's bodies, bound to proteins.
- This suggests an acquired "thyroid follicle-like" structure in the thymus responsible for iodine uptake.
Implications:
- Cystic Hassall's bodies possess iodine-trapping capabilities, mimicking thyroid tissue.
- This phenomenon can lead to misinterpretation of mediastinal radioiodine uptake in patients.
- Understanding this thymic function is vital for accurate diagnosis and treatment monitoring in thyroid cancer patients.