False-positive radioiodine uptake after radioiodine treatment in differentiated thyroid cancer.

Background And Purpose: False-positive radioiodine uptake can sometimes be observed with post-radioiodine treatment (RIT) whole body scanning. Radioiodine pitfall has often been reported as being caused by benign or inflammatory disease, or, in some cases, by tumor lesions. This paper reviews the possible causes of such false-positive imaging, and suggests possible reasons for suspecting these pitfalls.

Methods And Results: Online databases, including MEDLINE (via PubMed), Embase, ISI Web of Science, Google Scholar, and Scopus, were systematically examined, using different keyword combinations: "radioiodine false-positive imaging", "131 I false-positive imaging" and " RAI false-positive imaging". An illustrative case was described. Excluding cases in which SPECT/CT was not performed, a total of 18 papers was found: 17 case reports and one series regarding false-positive iodine-131 uptake after RIT.

Conclusions: The prevalence of radioiodine pitfall was significantly reduced through the use of SPECT/CT imaging, though its possible presence has always to be taken into account. Inflammation, passive iodine accumulation, other tumors, and, sometimes, unknown causes can all potentially generate false-positive imaging. Missing detection of false-positive imaging could result in over-staging and inappropriate RIT or it could lead to the non-detection of other cancers. We examine the reasons for these possible pitfalls.