Padma S*, Shanmuga Sundaram P and Firuz MD
Department of Nuclear Medicine & Petct, Amrita Institute of Medical Sciences, Cochin-6802041, Kerala, India
Received date: September 01, 2015 Accepted date: September 23, 2015Published date: September 26, 2015
Citation: Padma S, Sundaram PS, Firuz MD (2015) Bronchiectasis Masquerading as Lung Metastasis in a Patient with Papillary Carcinoma Thyroid Identified by 131I Whole Body Scintigraphy. J Nucl Med Radiat Ther 6:252. doi: 10.4172/2155-9619.1000252
Copyright: © 2015 Ayuka F, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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Differentiated thyroid carcinoma (DTC), arising from thyroid follicular epithelial cells, accounts for the vast majority of thyroid cancers. Despite being well-differentiated, papillary thyroid cancers may be overtly or minimally invasive. They may invade lymphatics but are less likely to invade blood vessels. Iodine-131 (131I) is routinely used to image patients after thyroidectomy to assess the presence of residual thyroid tissue with or without metastasis. False positive 131I scans, showing the presence of 131I uptake in the absence of residual thyroid tissue or metastases can occur, although they are uncommon. Unless recognized as a false positive, 131I uptake may result in diagnostic error and lead to administration of an unnecessary higher therapeutic dose. We present a 55 year old female, histopathologically proven case of follicular variant of papillary carcinoma that underwent Total Thyroidectomy. Residual thyroid and whole body scan showed moderate residual thyroid tissue with abnormal 131I in right lung masquerading as right lung metastases. SPECTCT (single photon emission computed tomography – computed tomography) was incremental in localizing the site of 131I uptake to bronchiectatic changes. 131I diagnostic and post therapy scans are useful to risk stratify DTC patients’ so that amount of high dose 131I to be administered to patient can be estimated and judiciously used in their treatment.
131I whole body scan; Differentiated thyroid carcinoma; Papillary carcinoma of thyroid; Bronchiectasis
55 year old female, histopathologically proven case of follicular variant of papillary carcinoma underwent Total Thyroidectomy. Macroscopically tumour was 2.5 × 0.7 cm, margins are free with no lymphovascular emboli or perinodal spread. Residual thyroid and whole body 131I scan was performed three weeks after the sugery. TSH was above 30 uIU/ml on the day of 131I administration. Patient was also on iodine restricted diet and was off seafoods for three weeks prior to scan. Whole body and static anterior neck images showed moderate residual thyroid tissue with abnormal 131I in right lung mimicking metastases (Figure 1). SPECT CT was performed which localized the site of abnormal 131I uptake to cystic bronchiectatic changes in right lung. On close interrogation patient suffered repeated upper respiratory tract infection. Stimulated serum Thyroglobulin (sensitive marker for identifying metastases) was 2.32 ng/ml confirming moderate residual thyroid tissue with no distant metastases.
Figure 1: Residual thyroid and whole body 131I scan showed moderate residual thyroid tissue (thin dotted arrow) with abnormal 131I in right lung masquerading as metastases (thick arrow). Additional SPECT CT localized the site of abnormal 131I uptake to cystic bronchiectatic changes in right lung (thick arrow).
Patient was orally ablated with 2220 Megabecqueral (i.e 60 millicuries, mCi) of 131I based on SPECTCT and Tg value. SPECTCT of thorax was incremental in localizing the 131I uptake to bronchiectatic changes to right lung. Otherwise patient would require higher doses of 131I for therapy (5550 Mbq, or 150 mCi) for lung metastases which is not only expensive but is an over treatment to this patient and produce higher radiation exposure. Post therapy 131I scan performed (Figure 2) on day 5 revealed significant 131I uptake in thyroid bed as expected in a post therapy setting.
Figure 2: Post therapy 131I scan performed on day 5 revealed significant 131Iuptake in thyroid bed as expected in a post therapy setting. However there was new 131I uptake in left lung field which was against the previous finding of right lung involvement. SPECTCT of thorax in post therapy setting showed corresponding cystic bronchiectatic changes in bilateral lungs suggesting new left lung infection/inflammation.
However there was new 131I uptake in left lung field which was against the previous finding of right lung involvement. SPECTCT of thorax in post therapy setting was performed which showed corresponding cystic bronchiectatic changes in bilateral lungs suggesting new left lung infection or inflammation. Thus 131I diagnostic and post therapy scans are useful to risk stratify patients’ so that amount of high dose 131I to be administered to patient can be estimated and judiciously used in their treatment. It is also useful to identify any sites of occult metastases.
131I is popularly termed the ‘magic bullet’ in the management of differentiated thyroid cancer for several years. SPECTCT in this setting is emerging as a useful tool in accurately localizing sites of pathological uptake and physiological mimics of disease, thus providing more accurate staging prognostic information for risk stratification, which in turn tailors management and follow-up regimes . Thyrocytes retain the ability to trap iodine, and various isotopes of Iodine can be used both diagnostically and therapeutically in the management of DTC . The correct interpretation of 131I scans is critical in the appropriate management of patients with thyroid cancer. False positive findings do occur. A radioiodine scan showing abnormal uptake outside the thyroid bed must be studied carefully and alternative reasons for the finding must be considered. False-positive localizations of 131I due to body secretions, pathologic exudate, activity in nonlactating breast, salivary gland inflammation, ovarian teratoma have been described . The prognosis of PTC and follicular thyroid cancer are almost similar.
Our case, demonstrates an important pitfall in the interpretation of 131I scintigraphy in DTC patients. It calls attention to the fact that 131I uptake may be related to various infectious and inflammatory processes, but infrequently with bronchiectasis, particularly with SPECTCT confirmation. In our patient incidentally there was progressive benign lung disease which misled diagnosis in two instances i.e. diagnostic and postherapy whole body 131I scan thus representing a potential pitfall. So any focus of 131I uptake must be looked upon carefully which will be worthwhile in the long run in deciding patient management.