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Delusory Radioiodine Uptake in Endometriotic Ovarian Cyst
Address for correspondence: Dr. Farinaz Farhoudi, Student Research Committee, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran. E-mail: farhoudif.ff@gmail.com
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Received: ,
Accepted: ,
This article was originally published by Wolters Kluwer - Medknow and was migrated to Scientific Scholar after the change of Publisher.
Abstract
A 25-year-old woman with a known case of papillary thyroid carcinoma conventional type referred to our center for treatment with radioactive iodine after total thyroidectomy. She received 200 mCi of radioiodine, and in the whole-body scan 1 week after the radioiodine therapy, an area of increased absorption was seen on the right side of the pelvis, which was diagnosed as an endometriotic ovarian cyst in the follow-up examinations.
Keywords
Endometriotic ovarian cyst
false-positive radioactive iodine uptake
I-131 whole-body scan
ovarian cyst
Introduction
The management of patients diagnosed with differentiated thyroid carcinoma typically involves the surgical removal of the entire thyroid gland, followed by the administration of radioactive iodine therapy. To evaluate the possible presence of metastasis to the neck and other parts of the body, a whole-body scan and measurement of blood serum thyroglobulin level are used.[1] Understanding the underlying factors contributing to the erroneous uptake of radioactive iodine is crucial for preventing unnecessary additional examinations. Here, we report a case of false-positive radioiodine uptake in an endometriotic cyst of the right ovary.
Case Report
A 25-year-old woman, known case of papillary thyroid carcinoma conventional type, has been referred to this center for treatment with radioactive iodine after total thyroidectomy. She received 200 mCi of radioiodine for the second time due to rising thyroglobulin levels (Tg>500ng/ml) and in the scan 1 week after the radioactive iodine therapy, an area of radioiodine accumulation was seen on the right side of the pelvis [Figure 1]. To rule out the possibility of metastasis in the pelvic cavity, single-photon emission computed tomography (CT)-CT was done in which radioiodine accumulation was localized in a cystic lesion in the right adnexa, in favor of an ovarian cyst [Figure 2]. Further evaluation with magnetic resonance (MR) images before and after intravenous gadolinium administration revealed a cystic lesion in the right adnexa measuring 19 mm, which shows hyperintensity on T1-weighted images and hypointensity (shading) on T2-weighted images. The shading sign is a characteristic pattern of endometriotic cysts at MR imaging [Figure 3].
Discussion
Following a complete removal of the thyroid, patients undergo an I-131 whole-body scan to detect any remaining thyroid tissue or signs of cancer spread. Posttreatment whole-body scans may reveal more areas of radioactive iodine uptake compared to the initial diagnostic scan in 6% to 13% of cases.[1] The sodium iodide symporter (NIS) is a strong transporter of iodine, responsible for concentrating radioiodine into the active thyroid tissue.[23] NIS is also found in salivary glands and gastric mucosa,[4] resulting in the uptake of radioactive iodine at these locations. Iodine is eliminated through the urinary system, resulting in physiological absorption in the kidneys and bladder. In addition to these physiological locations, some nonthreatening conditions may also exhibit higher RAI avidity, including blockage of the nasolacrimal duct, thymus, Meckel’s diverticulum, cysts in the liver and kidneys, adrenal adenoma, vascular aneurysms, and nabothian cysts.[256] While uncommon, the literature has documented instances of RAI uptake in different types of ovarian cysts, including endometrioid cysts, mucinous ovarian cystadenomas, dermoid cysts, and simple ovarian cysts.[7891011] Receiving the lowest dose rate is one of the most important concerns in iodine therapy[12] so it is crucial to distinguish between these noncancerous conditions and metastases to prevent unnecessary treatments and exposure to radioactive iodine.
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.
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