Diagnostic issues in Radioiodine Whole Body Scan: distribution and mechanisms of tracer uptake unrelated to thyroid cancer

Objectives 1. To provide an overview of unsuspected radioiodine (RAI) uptake in whole body scan (WBS) leading to diagnostic misinterpretation. 2. To demonstrate cases of abnormal RAI uptake in the absence of metastatic disease due to thyroid cancer. 3. To analyze the underlying mechanisms of RAI uptake in non-thyroidal malignancies and other pathologic tissues. Abstract Body: Differentiated thyroid cancer (DTC) represents over 90% of thyroid malignant tumors. Effective DTC management includes RAI administration either for diagnostic or therapeutic purposes. Diagnostic and post-treatment WBS represent an essential tool in the detection of remnant functioning thyroid tissue or metastatic disease. However, the ability of this procedure to detect local disease or distant metastases is compromised by the non-specific RAI localization in body sites other than thyroid tissue. Therefore, the knowledge of benign diseases and benign or malignant non-thyroidal tumors accumulating RAI could greatly enhance the interpretation of the study. In this exhibit, variants of abnormal RAI uptake will be introduced while selected cases from our departments will be presented. We will also discuss the mechanisms underlying abnormal RAI distribution.

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