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

Abstract

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.

Diagnostic Performance of [18F]TFB PET/CT Compared with Therapeutic Activity [131I]Iodine SPECT/CT and [18F]FDG PET/CT in Recurrent Differentiated Thyroid Carcinoma

“…Moreover, RAI has a variety of dose-dependent acute and long-term side effects, like adverse effects on the salivary and lacrimal glands up to secondary malignancies after repeated high activity of RAI ( 24 , 25 ). Also, it is well known that with increasing [ 131 I]iodine activity, more nontumor-related accumulations occur ( 26 , 27 ). These false-positive findings may lead to unnecessary further invasive procedures as biopsies ( Fig.…”

Concurrent Benign Iodine-Avid Thymic and Liver Cysts Mimicking Metastatic Disease on 131I Whole-Body Scintigraphy

“…After 6 years of clinic follow-up, the serum Tg remains <1.0 μg/L, and she remains asymptomatic and free of disease recurrence. 131 I accumulation in cysts has been reported in the literature involving many sites such as epithelial conjunctival inclusion cyst, 1 epidermal cyst, 2 thymus, 3–6 thyroglossal duct, 5 bronchogenic cyst, 4,5,7,8 breast, 5,7 liver, 4,5 hepatic hydatid cyst, 7 renal, 4,5,7,9 ovary, 4,5,9 bone, 9 uterine menstruation dermoid cyst, 9 pleuropericardial, 4,5 sebaceous cyst, 4,5,7 nasolacrimal duct, 4,5 laryngeal cyst, 4 gastrointestinal duplication cyst, 4 nabothian cyst, 4,10 and pancreatic lymphoepithelial cyst 11 . The postulated mechanism of 131 I uptake in the cysts varies and includes incomplete active transport or passive diffusion of the chemical materials and 131 I between the cyst and adjacent tissue followed by its retention within the cystic structure, 5,10–12 chronic inflammation resulting in hypervascularity and increased capillary permeability, 13,14 expression of sodium-iodide symporter in the cystic epithelial cells, 13,15 and organification of 131 I in leukocytes 14 .…”