ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

Endocrine Abstracts (2019) 63 GP88 | DOI: 10.1530/endoabs.63.GP88

An analysis of false-positive uptake on radioiodine whole-body scintigraphy

Ozlem Turhan Iyidir1, Pırıl Büyükaşık2, Adam Rajab Mwinyi2, Ayse Aktas3, Arzu Gencoglu3 & Neslihan Bascil Tutuncu1

Baskent University, Department of Endocrinology and Metabolism, Ankara, Turkey; 2Baskent University, Department of Internal Medicine, Ankara, Turkey; 3Baskent University, Department of Nuclear Medicine, Ankara, Turkey.

Introduction: Radioiodine can be used for the ablation/treatment and imaging of thyroid cancer. However, radioiodine uptake is not specific for thyroid tissue. Iodine-131 can show physiologic accumulation in several organs as breast, thymus, liver and gastrointestinal tract, or in benign conditions, such as cysts and inflammation, or in a variety of benign and malignant non-thyroidal tumors, which could be mistaken for thyroid cancer or cancer metastasis. Here we aimed to evaluate extrathyroidal uptakes in radioiodine scan of our patients with differantiated thyroid cancer.

Patients and methods: We reviewed the data of 701 planar 131I whole-body imaging findings of consecutive 585 patients with differantiated thyroid cancer. The patients were referred either for initial post-surgical 131I ablation, for subsequent 131I therapy of residual, recurrent or metastatic disease or for diagnostic 131I whole-body imaging after initial treatment. We evaluated the false-positive uptake of radioiodine in the whole body and noted the confirmed diagnosis of the incidental finding with further imaging modalities.

Results: Of the 585 patients, 214 (36.6%) had diagnostic whole body scan during their follow up for thyroid cancer, 255 (43.6%) had scans after radioiodine remnant ablation or adjuvant therapy, 116 (%19.8) had both diagnostic and posttreatment scans. The extrathryoidal uptakes are listed in Table 1. Of the 701 planar 131I whole-body imaging, 365 (62.4%) showed no incidental findings. The most commonly reported incidental finding was dental pathology (n=82; 14%).

Extrathyroidal uptakeN; %
None 365; 62.4%
Dental pathology 82; 14%
Sialoadenitis 50; 8.6%
Nasal inflammation 62; 10.6%
Bronchopulmonary infection-Bronchiectasis 17; 2.9%
Esophageal retention-Gastroeosophagial reflux disease11; 1.9%
Arthritis 5; 0.9%
Liver5; 0.9%
Non lactating breast (fibroadenoma; breast cancer)4; 0.7%
Thymus4; 0.7%
Trauma 3; 0.5%
Inguinal hernia3; 0.5%
Thryoglossal duct2; 0.3%
Ovarian cyst 1; 0.2%

Discussion: In our study we detailed the extrathyroidal uptake of diagnostic or posttherapy whole body scan of our patients with differentiated thyroid cancer which majority of them considered to be physiologic. Most commonly encountered uptake appeared in the oral cavity and was thought to be due to dental pathology. Further imaging was necessary in only a minority of patients. The awareness of these findings will lead us to be in contact with imaging physcians for characterizing the increased uptakes with additional imaging tehcniques and we can be more confident in establishing proper management for patients with differantiated thyroid cancer.

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