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E-JCRT CORRESPONDENCE
Year : 2015  |  Volume : 11  |  Issue : 3  |  Page : 656

Image findings of a false positive radioactive iodine-131 uptake mimicking metastasis in pulmonary aspergillosis identified on single photon emission computed tomography-computed tomography


Department of Nuclear Medicine and PET/CT, Comprehensive Cancer Care Centre, Kovai Medical Centre and Hospital Limited, Coimbatore, Tamil Nadu, India

Date of Web Publication9-Oct-2015

Correspondence Address:
Kamaleshwaran Koramadai Karuppusamy
Department of Nuclear Medicine, PET/CT and Radionuclide Therapy, Comprehensive Cancer Care Centre, Kovai Medical Centre and Hospital Limited, Coimbatore - 641 014, Tamil Nadu
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0973-1482.139271

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 > Abstract 

High doses of iodine-131 are commonly used in patients with differentiated thyroid cancer after total or subtotal thyroidectomy, in order to ablate the remaining cancer or normal thyroid tissue. Multiple different false-positive scans can occur in the absence of residual thyroid tissue or metastases. The authors present a case of abnormal uptake of radioactive iodine in the aspergilloma, potentially masquerading as pulmonary metastases.

Keywords: Aspergillosis, lung uptake, radioiodine, single-photon emission computerized tomography computerized tomography


How to cite this article:
Karuppusamy KK, Antony J, Radhakrishnan E R, Shinto AS. Image findings of a false positive radioactive iodine-131 uptake mimicking metastasis in pulmonary aspergillosis identified on single photon emission computed tomography-computed tomography. J Can Res Ther 2015;11:656

How to cite this URL:
Karuppusamy KK, Antony J, Radhakrishnan E R, Shinto AS. Image findings of a false positive radioactive iodine-131 uptake mimicking metastasis in pulmonary aspergillosis identified on single photon emission computed tomography-computed tomography. J Can Res Ther [serial online] 2015 [cited 2019 Jun 20];11:656. Available from: http://www.cancerjournal.net/text.asp?2015/11/3/656/139271


 > Introduction Top


Whole-body scans (WBSs) based on diagnostic or therapeutic doses of iodine-131 (I-131) can visualize metastatic lesions in thyroid cancer patients who have undergone total thyroidectomy. However, a variety of unusual lesions may cause false-positive results, and therefore, careful evaluation of abnormal scans is imperative to avoid unnecessary surgical removal or high-dose radioiodine treatment. Here, we report a patient with pulmonary aspergilloma mimicking metastasis of thyroid cancer on WBS.


 > Case report Top


A 44-year-old female underwent a total thyroidectomy, bilateral modified radical neck dissection and paratracheal lymph node dissection for differentiated thyroid cancer (DTC) of the papillary type on the right lobe and bilateral neck metastasis. Histopathology revealed extrathyroid extension of the cancer, bilateral neck and in one paratracheal lymph node metastasis. Thyroid function tests 4 weeks after surgery were thyrotropin >100 μIU/ml, thyroglobulin was 0.2 ng/ml and antithyroglobulin antibody was 1.29 U/ml.

The patient underwent pretherapy I-131 WBS, which showed residual thyroid tissue in thyroid bed. I-131 ablation with 5.55 GBq of I-131 was administered and WBS was obtained after 5 days.

The WBS demonstrated usual I-131 accumulation in the thyroid remnant, the salivary glands and the liver. Increased I-131 uptake in the left lung was also noted [Figure 1]. The patient had a history of tuberculosis. Single-photon emission computerized tomography computerized tomography (SPECT-CT) scan of the chest showed increased uptake in the fibrosis with traction bronchiectasis in the left upper lobe. CT showed soft tissue density lesion in one of the cavitary bronchiectasis suggestive of fungal ball [Figure 2]. A subsequent blood test for precipitating antibodies to Aspergillus antigens produced a result of 35 U/ml (reference range: 0-8 U/ml).The patient was clinically diagnosed as having pulmonary aspergilloma based on serologic test and radiologic imaging results.
Figure 1: Whole body iodine-131 scan shows uptake in thyroid remnant, left chest and physiological uptake in salivary glands and liver

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Figure 2: Single-photon emission computerized tomography/ computerized tomography (CT) of chest showing increased uptake in the fibrosis with traction bronchiectasis in the left upper lobe. CT showed soft tissue density lesion in one of the cavitaty bronchiectatis suggestive of fungal ball

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 > Discussion Top


Iodine-131 WBS based on diagnostic or therapeutic doses of I-131 can visualize metastatic lesions in thyroid cancer patients who have undergone total thyroidectomy. [1] However, a variety of unusual lesions may cause a false positive result on the radioiodine WBS and so careful evaluation of an abnormal scan is imperative to appropriately manage patients with DTC. [2],[3] The decision to administer radioiodine treatment is mainly based on the diagnostic scan, and misinterpretation of physiological or other causes of radioiodine uptake as metastatic thyroid cancer could lead to the decision to perform unnecessary surgical removal or to administer a high dose of I-131, which results in fruitless radiation exposure. Therefore, correct interpretation of the diagnostic scan is critical for the proper management. [4]

A variety of inflammatory and infectious disease can have radioiodine accumulation by increased blood flow that delivers increased levels of radioiodine to the site, and enhanced permeability of the capillary that increases diffusion of the tracer to the extracellular water space. Radioiodine accumulation in bronchiectasis and pulmonary aspergilloma has been reported. [5],[6] SPECT/CT with radioiodine can demonstrate a higher number of radioiodine uptake lesions, and it can more correctly differentiate between physiologic and pathologic uptakes, and so it permits a more appropriate therapeutic approach to be selected. [7],[8]

 
 > References Top

1.
American Thyroid Association (ATA) Guidelines Taskforce on Thyroid Nodules and Differentiated Thyroid Cancer, Cooper DS, Doherty GM, Haugen BR, Kloos RT, Lee SL, et al. Revised American Thyroid Association management guidelines for patients with thyroid nodules and differentiated thyroid cancer. Thyroid 2009;19:1167-214.  Back to cited text no. 1
    
2.
Mitchell G, Pratt BE, Vini L, McCready VR, Harmer CL. False positive 131I whole body scans in thyroid cancer. Br J Radiol 2000;73:627-35.  Back to cited text no. 2
    
3.
Carlisle MR, Lu C, McDougall IR. The interpretation of 131I scans in the evaluation of thyroid cancer, with an emphasis on false positive findings. Nucl Med Commun 2003;24:715-35.  Back to cited text no. 3
    
4.
Shapiro B, Rufini V, Jarwan A, Geatti O, Kearfott KJ, Fig LM, et al. Artifacts, anatomical and physiological variants, and unrelated diseases that might cause false-positive whole-body 131-I scans in patients with thyroid cancer. Semin Nucl Med 2000;30:115-32.  Back to cited text no. 4
    
5.
Ahn BC, Lee SW, Lee J, Kim C. Pulmonary aspergilloma mimicking metastasis from papillary thyroid cancer. Thyroid 2011;21:555-8.  Back to cited text no. 5
    
6.
Jong I, Taubman K, Schlicht S. Bronchiectasis simulating pulmonary metastases on iodine-131 scintigraphy in well-differentiated thyroid carcinoma. Clin Nucl Med 2005;30:688-9.  Back to cited text no. 6
    
7.
Spanu A, Solinas ME, Chessa F, Sanna D, Nuvoli S, Madeddu G. 131I SPECT/CT in the follow-up of differentiated thyroid carcinoma: Incremental value versus planar imaging. J Nucl Med 2009;50:184-90.  Back to cited text no. 7
    
8.
Thust S, Fernando R, Barwick T, Mohan H, Clarke SE. SPECT/CT identification of post-radioactive iodine treatment false-positive uptake in a simple renal cyst. Thyroid 2009;19:75-6.  Back to cited text no. 8
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