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False-positive radioiodine whole-body scan due to a renal cyst
Affiliations- Department of Endocrinology, Metabolism, and Internal Medicine, Poznan University of Medical Sciences, Poznan, Poland
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Abstract
Patients affected by differentiated thyroid cancer are treated surgically and by ablative radioiodine therapy. A post-therapy whole-body scan allows detection of thyroid remnants or local and distant metastases, although false-positive findings may be observed. We report a case of a 75-year-old woman with follicular thyroid cancer, who underwent ablative radioiodine treatment. On post-therapy wholebody scan, abnormal uptake in the left upper abdomen was found, although stimulated thyroglobulin level was not suggestive for distant metastases of differentiated thyroid carcinoma. Additional SPECT/CT acquisition revealed focal 131I uptake located at the posterolateral wall of the left kidney corresponding to a round lesion 47 mm in maximal diameter. In order to verify this finding abdominal ultrasound and abdominal contrast-enhanced CT were performed, confirming multiple renal cysts in the left kidney; the largest one was the site of abnormal radioiodine accumulation. Despite the high incidence of renal cysts, especially in the elderly, radioiodine uptake in renal cysts
is extremely rare. Different hypotheses on the mechanism of radioiodine uptake in the cyst were proposed, among them active secretion by sodium-iodide symporter or other transporting proteins. We conclude that abnormal radioiodine uptake in renal cysts can be an exceptional finding mimicking a metastasis.
Abstract
Patients affected by differentiated thyroid cancer are treated surgically and by ablative radioiodine therapy. A post-therapy whole-body scan allows detection of thyroid remnants or local and distant metastases, although false-positive findings may be observed. We report a case of a 75-year-old woman with follicular thyroid cancer, who underwent ablative radioiodine treatment. On post-therapy wholebody scan, abnormal uptake in the left upper abdomen was found, although stimulated thyroglobulin level was not suggestive for distant metastases of differentiated thyroid carcinoma. Additional SPECT/CT acquisition revealed focal 131I uptake located at the posterolateral wall of the left kidney corresponding to a round lesion 47 mm in maximal diameter. In order to verify this finding abdominal ultrasound and abdominal contrast-enhanced CT were performed, confirming multiple renal cysts in the left kidney; the largest one was the site of abnormal radioiodine accumulation. Despite the high incidence of renal cysts, especially in the elderly, radioiodine uptake in renal cysts
is extremely rare. Different hypotheses on the mechanism of radioiodine uptake in the cyst were proposed, among them active secretion by sodium-iodide symporter or other transporting proteins. We conclude that abnormal radioiodine uptake in renal cysts can be an exceptional finding mimicking a metastasis.
Keywords
follicular thyroid cancer; renal cyst; radioiodine; post-therapy whole-body scan
About this articleTitle
False-positive radioiodine whole-body scan due to a renal cyst
Journal
Issue
Article type
Case report
Pages
736-739
Published online
2018-10-11
Page views
3545
Article views/downloads
1207
DOI
Pubmed
Bibliographic record
Endokrynol Pol 2018;69(6):736-739.
Keywords
follicular thyroid cancer
renal cyst
radioiodine
post-therapy whole-body scan
Authors
Adam Maciejewski
Rafał Czepczyński
Marek Ruchała
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