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Year : 2020  |  Volume : 35  |  Issue : 1  |  Page : 76-77  

Iodine uptake in retroperitoneal cysts after radioactive iodine treatment


1 Department of Nuclear Medicine, Jeju National University Hospital, Jeju National University School of Medicine, Jeju-si, Republic of Korea
2 Department of Internal Medicine, Jeju National University Hospital, Jeju National University School of Medicine, Jeju-si, Republic of Korea
3 Department of Radiology, Jeju National University Hospital, Jeju National University School of Medicine, Jeju-si, Republic of Korea

Date of Submission29-Sep-2019
Date of Acceptance16-Oct-2019
Date of Web Publication31-Dec-2019

Correspondence Address:
Prof. Hee-Sung Song
Department of Nuclear Medicine, Jeju National University Hospital, Jeju National University School of Medicine, Aran 13gil 15, Jeju-si 63241
Republic of Korea
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijnm.IJNM_181_19

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   Abstract 


Radioactive iodine ablation has long-lasting effects on remnant thyroid tissue and metastasis from well-differentiated thyroid cancer. After radioactive iodine treatment, scintigraphy is a major imaging modality for detecting metastasis and assessing its management. False-positive iodine uptake can be found in many aberrant locations, including cysts. This report describes iodine uptake in retroperitoneal cysts in a 62-year-old woman diagnosed with papillary thyroid carcinoma. Radioiodine scintigraphy was performed after iodine therapy. Abnormally increased iodine activity was noted in the left upper abdomen. Additional radiologic examinations helped in preventing invasive biopsy.

Keywords: False-positive finding, iodine-131, radioiodine scintigraphy, radioiodine single-photon emission computed tomography/computed tomography, retroperitoneal cysts


How to cite this article:
Lee JY, Song HS, Choi JH, Lee JS. Iodine uptake in retroperitoneal cysts after radioactive iodine treatment. Indian J Nucl Med 2020;35:76-7

How to cite this URL:
Lee JY, Song HS, Choi JH, Lee JS. Iodine uptake in retroperitoneal cysts after radioactive iodine treatment. Indian J Nucl Med [serial online] 2020 [cited 2020 Jan 26];35:76-7. Available from: http://www.ijnm.in/text.asp?2020/35/1/76/274373



A 62-year-old woman with a history of breast cancer and a pancreatic cyst was newly diagnosed with papillary thyroid carcinoma that was incidentally detected on F-18 fluorodeoxyglucose positron emission tomography/computed tomography (CT) performed for breast cancer staging. She underwent total thyroidectomy with bilateral neck lymph node dissection. During surgery, a gross extrathyroidal extension invading the strap muscles was observed, with metastasis in one out of six lymph nodes (T3b N1a). Considering the high risk of disease recurrence as per the American Thyroid Association 2015 Risk Stratification System,[1] she received radioactive iodine therapy with 3.7 GBq (100 mCi) of iodine-131 (I-131) for ablation of the remnant thyroid tissue 4 months later. Seven days later, a whole-body iodine scan was obtained [Figure 1]. Focal radioactivity was observed in the anterior neck area, suggesting remnant thyroid tissue. Abnormal focal uptake was seen in the left upper abdomen. Remaining iodine uptake was unremarkable. Laboratory examination revealed a free thyroxin level of 1.47 (normal range: 0.93–1.70) ng/dl, thyroid-stimulating hormone level of 104.9 (normal range: 0.27–4.20) IU/ml, thyroglobulin antigen level of 0.04 (normal range: 3.5–77.0) ng/mL, and thyroglobulin antibody titer of 10.0 (normal range: 0–115) IU/ml.
Figure 1: Postoperative iodine-131 scintigraphy shows radiotracer uptake in the neck area and in the left upper abdomen (a: anterior; b: posterior)

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Single-photon emission CT/CT (SPECT/CT) was used to verify iodine uptake in the left abdomen. Iodine uptake was observed in the posterior aspect of the left kidney [Figure 2]a. This activity corresponded to round soft-tissue densities in the left retroperitoneum on nonenhanced CT images obtained during SPECT/CT [Figure 2]b. Contrast-enhanced abdominopelvic CT, which was performed for the evaluation of a pancreatic cyst 4 months back, revealed nonenhancing lesions with low attenuation [Figure 2]c. The retroperitoneal cysts showed no enhancement or interval change in size; this suggested the presence of benign lesions. High signal intensity on T2-weighted abdominal magnetic resonance imaging performed for follow-up evaluation of the pancreatic cyst revealed that the multiloculated cystic lesion at the left posterior pararenal space was a cystic lymphangioma [Figure 2]d. False-positive iodine uptake can occur in many aberrant locations, including cystic lesions. Previous reports have shown iodine uptake in cystic structures, including bronchogenic, hepatic, renal, thymic, ovarian, and ganglion structures.[2],[3],[4],[5],[6],[7],[8],[9],[10],[11],[12] The mechanism may involve passive diffusion and retention of iodine in cysts. Our report demonstrates rare SPECT/CT images of iodine uptake in retroperitoneal cysts. Additional radiologic examinations helped in preventing invasive biopsy in this case.
Figure 2: The transaxial single-photon emission computed tomography image reveals that iodine uptake occurred in the posterior aspect of the left kidney (a and b). This lesion is observed as nonenhancing low-attenuated soft-tissue density on contrast-enhanced abdominopelvic computed tomography scan (c) and high signal intensity on T2-weighted abdominal magnetic resonance imaging (d), suggesting a benign lesion

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Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
   References Top

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Haugen BR, Alexander EK, Bible KC, Doherty GM, Mandel SJ, Nikiforov YE, et al. 2015 American thyroid association management guidelines for adult patients with thyroid nodules and differentiated thyroid cancer: The American thyroid association guidelines task force on thyroid nodules and differentiated thyroid cancer. Thyroid 2016;26:1-33.  Back to cited text no. 1
    
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Lejeune M, Héron C, Tenenbaum F, Sarfati PO, Louvel A, Luton JP, et al. Iodine 131 uptake by a bronchogenic cyst in a patient with differentiated carcinoma of the thyroid gland. Presse Med 2000;29:1345-7.  Back to cited text no. 3
    
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Maciejewski A, Czepczyński R, Ruchała M. False-positive radioiodine whole-body scan due to a renal cyst. Endokrynol Pol 2018;69:736-9.  Back to cited text no. 5
    
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Campennì A, Ruggeri RM, Giovinazzo S, Sindoni A, Santoro D, Baldari S. Radioiodine uptake in a renal cyst mimicking a metastasis in a patient affected by differentiated thyroid cancer: Case report and review of the literature. Ann Nucl Med 2014;28:472-6.  Back to cited text no. 6
    
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Demir Y, Üçler R, Alkiş İ, Bulut G. Accurately localizing the thyroid tissue in mature cystic teratoma of ovary by single-photon emission computerized tomography/computerized tomography. Indian J Nucl Med 2015;30:364-5.  Back to cited text no. 8
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Basu S, Mahajan A. Ovarian dermoid cyst serendipitously detected by pelvic radioiodine-(131) I uptake and by diffusion weighted MRI in a post-thyroidectomy case of papillary thyroid carcinoma. Hell J Nucl Med 2013;16:62-3.  Back to cited text no. 9
    
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Flug J, Lameka K, Lee R, Katz DS, Sung WW, Yung E. False-positive I-131 uptake by an ovarian serous cystadenofibroma. Clin Nucl Med 2012;37:178-80.  Back to cited text no. 10
    
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Yazici B, Oral A, Omur O, Yazici A. Radioiodine uptake in an ovarian mature teratoma detected with SPECT/CT. Clin Nucl Med 2015;40:e157-60.  Back to cited text no. 11
    
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Khasgiwala A, Friedman KP, Ghesani M, Raad RA. Ganglion cyst on 131I whole-body scintigraphy. Clin Nucl Med 2017;42:e58-60.  Back to cited text no. 12
    


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