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Radioactive Iodine Scintiphotos of a Man With Thyroid Cancer

Fed Pract. 2014 November;31(11):40-42

References

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2. Carlisle MR, Lu C, McDougall IR. The interpretation of 131I scans in the evaluation of thyroid cancer, with an emphasis on false positive findings. Nucl Med Commun. 2003;24(6):715-735.

3. Shapiro B, Rufini V, Jarwan A, et al. Artifacts, anatomical and physiological variants, and unrelated diseases that might cause false-positive whole-body 131-I scans in patients with thyroid cancer. Semin Nucl Med. 2000;30(2):115-132.

4. Mitchell G, Pratt BE, Vini L, McCready VR, Harmer CL. False positive 131I whole body scans in thyroid cancer. Br J Radiol. 2000;73(870):627-635.

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6. Pena Pardo FJ, Crespo de la Jara A, Fernández Morejón FJ, Sureda González M, Forteza Vila J, Brugarolas Masllorens A. Solitary focus in the liver in a thyroid cancer patient after a whole body scan with 131 iodine. Rev Esp Med Nucl. 2007;26(5):294-296.

7. Omür O, Ozbek SS, Akgün A, Yazici B, Mutlukoca N, Ozcan Z. False-positive I-131 accumulation in a hepatic hydatid cyst. Clin Nucl Med. 2007;32(12):930-932.

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Our Treatment

The patient had no pain in the area and, upon further questioning, reported that he returned wearing the same athletic shorts. Given that radioiodine is excreted in the urine, this atypical distribution was thought to reflect urinary contamination. When images were taken again with the shorts removed, no abnormal radioiodine activity was present (see Figures 2C and 2D). Additional findings with thyrotropin alfa stimulation included increased quantitative thyroglobulin values of 20.2 ng/mL with antithyroglobulin antibody < 20.0 U/mL. Radioiodine ablation therapy using thyrotropin alfa was repeated. Iodine localization also was not present in the hip on posttherapy imaging (not shown).

Despite advances in imaging techniques, radioiodine scanning remains an imperfect science. Artifacts and pitfalls have been identified; in part, these are related to the accumulation of iodide in organs other than the thyroid, such as the nasopharynx and stomach, as well as the apparent accumulation due to excretion in the gut and bladder.^2-4 These variations can be divided into ectopic normal thyroid tissue, physiologic accumulation in nonthyroidal tissue, and contamination by physiologic secretions. Recent case reports have confirmed this classification. Abnormal radioiodine uptake has been described in vertebral hemangioma,⁵ liver abscess⁶ and hydatid cyst,⁷ bronchiectasis,⁸ bronchogenic cyst and mucinous cystadenoma (2 fluid-filled cavities),⁹ chronic submandibular sialadenitis,¹⁰ esophageal diverticulum,¹¹ hiatal hernia,¹² appendix,¹³ indwelling Hickman catheter,¹⁴ renal cyst,¹⁵ and, similar to this case, contamination of the hair.¹⁶

Contaminated clothing is not uncommon; however, a persistent abnormality from contaminated clothing on repeat follow-up is unusual and could easily be misinterpreted.² It would be valuable for all providers to be aware of the pitfalls of imaging before embarking on an unnecessary and potentially hazardous—not to mention costly—treatment course.

Acknowledgments
The authors acknowledge the assistance of Richard Cacciato, MLIS, Medical Librarian, who assisted in the literature review.

Author disclosures
The authors report no actual or potential conflicts of interest with regard to this article.

Disclaimer
The opinions expressed herein are those of the authors and do not necessarily reflect those of Federal Practitioner, Frontline Medical Communications Inc., the U.S. Government, or any of its agencies. This article may discuss unlabeled or investigational use of certain drugs. Please review the complete prescribing information for specific drugs or drug combinations—including indications, contraindications, warnings, and adverse effects—before administering pharmacologic therapy to patients.