False-Positive Uptake of Radioiodine in Renal Hamartoma in a Patient With Differentiated Thyroid Cancer

2017 ◽  
Vol 42 (9) ◽  
pp. 709-710 ◽  
Author(s):  
Guohua Shen ◽  
Zhongzhi Qi ◽  
Rui Huang ◽  
Bin Liu ◽  
Anren Kuang
Keyword(s):  
Thyroid Cancer ◽  
False Positive ◽  
Differentiated Thyroid Cancer ◽  
Renal Hamartoma

scholarly journals A False Positive I-131 Metastatic Survey Caused by Radioactive Iodine Uptake by a Benign Thymic Cyst

2017 ◽  
Vol 2017 ◽  
pp. 1-4
Author(s):  
Avneet K. Singh ◽  
Adina A. Bodolan ◽  
Matthew P. Gilbert
Keyword(s):  
Thyroid Cancer ◽  
False Positive ◽  
Differentiated Thyroid Cancer ◽  
Radioactive Iodine ◽  
Case Reports ◽  
Distant Metastases ◽  
The United States ◽  
Thymic Cyst ◽  
Pathological Findings ◽  
Thymic Cysts

Thyroid carcinoma is the most common endocrine malignancy in the United States with increasing incidence and diagnosis but stable mortality. Differentiated thyroid cancer rarely presents with distant metastases and is associated with a low risk of morbidity and mortality. Despite this, current protocols recommend remnant ablation with radioactive iodine and evaluation for local and distant metastasis in some patients with higher risk disease. There are several case reports of false positive results of metastatic surveys that are either normal physiologic variants or other pathological findings. Most false positive findings are associated with tissue that has physiologic increased uptake of I-131, such as breast tissue or lung tissue; pathological findings such as thymic cysts are also known to have increased uptake. Our case describes a rare finding of a thymic cyst found on a false positive I-131 metastatic survey. The patient was taken for surgical excision and the final pathology was a benign thymic cyst. Given that pulmonary metastases of differentiated thyroid cancer are rare, thymic cysts, though also rare, must be part of the differential diagnosis for false positive findings on an I-131 survey.

scholarly journals Serum Thyroglobulin (Tg) Monitoring of Patients with Differentiated Thyroid Cancer Using Sensitive (Second-Generation) Immunometric Assays Can Be Disrupted by False-Negative and False-Positive Serum Thyroglobulin Autoantibody Misclassifications

2014 ◽  
Vol 99 (12) ◽  
pp. 4589-4599 ◽  
Author(s):  
Carole Spencer ◽  
Ivana Petrovic ◽  
Shireen Fatemi ◽  
Jonathan LoPresti
Keyword(s):  
Thyroid Cancer ◽  
False Positive ◽  
Differentiated Thyroid Cancer ◽  
Operating Characteristic ◽  
Characteristic Curve ◽  
False Negative ◽  
False Negatives ◽  
Serum Thyroglobulin ◽  
Positive Serum ◽  
Operating Characteristic Curve

Context: Reliable thyroglobulin (Tg) autoantibody (TgAb) detection before Tg testing for differentiated thyroid cancer (DTC) is critical when TgAb status (positive/negative) is used to authenticate sensitive second-generation immunometric assay (2GIMA) measurements as free from TgAb interference and when reflexing “TgAb-positive” sera to TgAb-resistant, but less sensitive, Tg methodologies (radioimmunoassay [RIA] or liquid chromatography-tandem mass spectrometry [LC-MS/MS]). Objective: The purpose of this study was to assess how different Kronus (K) vs Roche (R) TgAb method cutoffs for “positivity” influence false-negative vs false-positive serum TgAb misclassifications that may reduce the clinical utility of reflex Tg testing. Methods: Serum Tg2GIMA, TgRIA, and TgLC-MS/MS measurements for 52 TgAb-positive and 37 TgAb-negative patients with persistent/recurrent DTC were compared. A total of 1426 DTC sera with TgRIA of ≥1.0 μg/L had false-negative and false-positive TgAb frequencies determined using low Tg2GIMA/TgRIA ratios (<75%) to indicate TgAb interference. Results: TgAb-negative patients with disease displayed Tg2GIMA, TgRIA, and TgLC-MS/MS serum discordances (% coefficient of variation = 24 ± 20%, range, 0%–100%). Of the TgAb-positive patients with disease, 98% had undetectable/lower Tg2GIMA vs either TgRIA or TgLC-MS/MS (P < .01), whereas 8 of 52 (15%) had undetectable Tg2GIMA + TgLC-MS/MS associated with TgRIA of ≥1.0 μg/L. Receiver operating characteristic curve analysis reported more sensitivity for TgAb method K vs R (81.9% vs 69.1%, P < .001), but receiver operating characteristic curve cutoffs (>0.6 kIU/L [K] vs >40 kIU/L [R]) had unacceptably high false-negative frequencies (22%–32%), whereas false positives approximated 12%. Functional sensitivity cutoffs minimized false negatives (13.5% [K] vs 21.3% [R], P < .01) and severe interferences (Tg2GIMA, <0.10 μg/L) (0.7% [K] vs 2.4% [R], P < .05) but false positives approximated 23%. Conclusions: Reliable detection of interfering TgAbs is method and cutoff dependent. No cutoff eliminated both false-negative and false-positive TgAb misclassifications. Functional sensitivity cutoffs were optimal for minimizing false negatives but have inherent imprecision (20% coefficient of variation) that, exacerbated by TgAb biologic variability during DTC monitoring, could cause TgAb status to fluctuate for patients with low TgAb concentrations, prompting unnecessary Tg method changes and disrupting Tg monitoring. Laboratories using reflexing should limit Tg method changes by considering a patient's Tg + TgAb testing history in addition to current TgAb status before Tg method selection.

scholarly journals Causes of False-Positive Radioactive Iodine Uptake in Patients with Differentiated Thyroid Cancer

2021 ◽  
Vol 9 (6) ◽  
Author(s):  
Karin Wu ◽  
Uzoezi Ozomaro ◽  
Robert Flavell ◽  
Miguel Pampaloni ◽  
Chienying Liu
Keyword(s):  
Thyroid Cancer ◽  
False Positive ◽  
Differentiated Thyroid Cancer ◽  
Radioactive Iodine ◽  
Imaging Modality ◽  
Whole Body ◽  
Cross Sectional ◽  
Cross Sectional Imaging ◽  
Patient’S History ◽  
Radioactive Iodine Uptake

Abstract Purpose Radioactive iodine (RAI) whole-body scan is a sensitive imaging modality routinely used in patients with differentiated thyroid cancer to detect persistent and recurrent disease. However, there can be false-positive RAI uptake that can lead to misdiagnosis and misclassification of a patient’s cancer stage. Recognizing the causes of false positivity can avoid unnecessary testing and treatment as well as emotional stress. In this review, we discuss causes and summarize various mechanisms for false-positive uptake. Recent Findings We report a patient with differentiated thyroid cancer who was found to have Mycobacterium avium complex infection as the cause of false-positive RAI uptake in the lungs. Using this case example, we discuss and summarize findings from the literature on etiologies of false-positive RAI uptake. We also supplement additional original images illustrating other examples of false RAI uptake. Summary False-positive RAI uptake may arise from different causes and RAI scans need to be interpreted in the context of the patient’s history and corresponding cross-sectional imaging findings on workup. Understanding the potential pitfalls of the RAI scan and the mechanisms underlying false uptake are vital in the care of patients with differentiated thyroid cancer.

scholarly journals Mediastinal Images Resembling Thymus Following 131-I Treatment for Thyroid Cancer

2005 ◽  
Vol 63 (2) ◽  
Author(s):  
L. Montella ◽  
M. Caraglia ◽  
A. Abbruzzese ◽  
A. Soricelli ◽  
M. Caputi ◽  
...  
Keyword(s):  
Differential Diagnosis ◽  
Thyroid Cancer ◽  
False Positive ◽  
Differentiated Thyroid Cancer ◽  
Thymic Hyperplasia ◽  
Whole Body ◽  
Serum Thyroglobulin ◽  
Pathological Tissues ◽  
Metastatic Thyroid Cancer

The follow-up of Differentiated Thyroid Cancer conventionally includes serum thyroglobulin and periodic Whole Body Scans. The uptake of 131-I in normal and pathological tissues different from metastatic thyroid cancer sites is a cause of false-positive scans. Among them, mediastinal uptake caused by thymic hyperplasia can be observed. The aim of the present study was to review a series of 573 patients with differentiated thyroid cancer treated with 131-I after surgery between 1992 and 2003 looking above all for those with mediastinal images resembling thymus. This evaluation is presented together with some hypotheses on the relationships between thymus and thyroid. Moreover, some considerations are made on the differential diagnosis between thymus and mediastinal tumour thyroid residues.

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