Thyroid Research and Practice

CASE REPORT
Year
: 2014  |  Volume : 11  |  Issue : 3  |  Page : 111--112

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


Koramadai Karuppusamy Kamaleshwaran, Joppy Antony, Edathuruthy Kalarickal Radhakrishnan, Ajit Sugunan Shinto 
 Department of Nuclear Medicine and Positron Emission Tomography/Computed Tomography, Comprehensive Cancer Care Centre, Kovai Medical Centre and Hospital Limited, Coimbatore, Tamil Nadu, India

Correspondence Address:
Koramadai Karuppusamy Kamaleshwaran
(Nuclear Medicine) Department of Nuclear Medicine, Positron Emission Tomography/Computed Tomography and Radionuclide Therapy, Comprehensive Cancer Care Centre, Kovai Medical Centre and Hospital Limited, Coimbatore 641 014, Tamil Nadu
India

Abstract

High doses of iodine-131 (I-131) are commonly used in patients with differentiated thyroid cancer (DTC) 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.



How to cite this article:
Kamaleshwaran KK, Antony J, Radhakrishnan EK, Shinto AS. Image findings of a false positive radioactive I-131 uptake mimicking metastasis in pulmonary aspergillosis identified on Single photon emission computed tomography-computed tomography.Thyroid Res Pract 2014;11:111-112


How to cite this URL:
Kamaleshwaran KK, Antony J, Radhakrishnan EK, Shinto AS. Image findings of a false positive radioactive I-131 uptake mimicking metastasis in pulmonary aspergillosis identified on Single photon emission computed tomography-computed tomography. Thyroid Res Pract [serial online] 2014 [cited 2021 Dec 2 ];11:111-112
Available from: https://www.thetrp.net/text.asp?2014/11/3/111/138556


Full Text

 INTRODUCTION



Whole body scans (WBSs) based on diagnostic or therapeutic doses of 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



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 adminstered 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 computed tomography-computed 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 cavitatory 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}{Figure 2}

 DISCUSSION



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 chosen. [7],[8]

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