Lee H, Chung YS, Lee JH, Lee KY, Hwang KH. Characterization of focal hypermetabolic thyroid incidentaloma: An analysis with F-18 fluorodeoxyglucose positron emission tomography/computed tomography parameters. World J Clin Cases 2022; 10(1): 155-165 [PMID: 35071515 DOI: 10.12998/wjcc.v10.i1.155]
Corresponding Author of This Article
Kyung-Hoon Hwang, MD, Professor, Department of Nuclear Medicine, Gachon University College of Medicine, Gil Medical Center, Namdong-daero 774 beon-gil, Namdong-gu, Incheon 21565, South Korea. forrest88@hanmail.net
Research Domain of This Article
Radiology, Nuclear Medicine & Medical Imaging
Article-Type of This Article
Retrospective Study
Open-Access Policy of This Article
This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Haejun Lee, Kyung-Hoon Hwang, Department of Nuclear Medicine, Gachon University College of Medicine, Gil Medical Center, Incheon 21565, South Korea
Yoo Seung Chung, Joon-Hyop Lee, Department of Endocrine Surgery, Gachon University College of Medicine, Gil Medical Center, Incheon 21565, South Korea
Ki-Young Lee, Department of Endocrinology and Metabolism, Gachon University College of Medicine, Gil Medical Center, Incheon 21565, South Korea
Author contributions: Lee H and Hwang KH contributed to this work; Lee H and Hwang KH designed the research study; Lee H, Chung YS, Lee JH, Lee KY and Hwang KH performed the research; Lee H contributed analytic tools; Lee H, Chung YS, Lee JH, Lee KY and Hwang KH analyzed the data and wrote the manuscript; and all authors have read and approved the final manuscript.
Institutional review board statement: This retrospective study was approved by the institutional review board of our hospital (IRB no. GAIRB2020-297), and the requirement to obtain informed consent was waived. The study was conducted in accordance with the 1964 Declaration of Helsinki and later amendments.
Informed consent statement: The requirement to obtain informed consent was waived.
Conflict-of-interest statement: The authors have no potential conflicts of interest to disclose.
Data sharing statement: Technical appendix, statistical code, and dataset available from the corresponding author at [forrest88@hanmail.net].
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Kyung-Hoon Hwang, MD, Professor, Department of Nuclear Medicine, Gachon University College of Medicine, Gil Medical Center, Namdong-daero 774 beon-gil, Namdong-gu, Incheon 21565, South Korea. forrest88@hanmail.net
Received: August 19, 2021 Peer-review started: August 19, 2021 First decision: September 29, 2021 Revised: October 9, 2021 Accepted: November 22, 2021 Article in press: November 22, 2021 Published online: January 7, 2022 Processing time: 133 Days and 4.4 Hours
Abstract
BACKGROUND
Incidentally found thyroid tumor (thyroid incidentaloma, TI) on F-18 fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET-CT) is reported in 2.5%-5% of patients being investigated for non-thyroid purposes. Up to 50% of these cases have been diagnosed to be malignant by cytological/histological results. Ultrasonography (US) and fine-needle aspiration cytology are recommended for thyroid nodules with high FDG uptake (hypermetabolism) that are 1 cm or greater in size. It is important to accurately determine whether a suspicious hypermetabolic TI is malignant or benign.
AIM
To distinguish malignant hypermetabolic TIs from benign disease by analyzing F-18 FDG PET-CT parameters and to identify a cut-off value.
METHODS
Totally, 12761 images of patients who underwent F-18 FDG PET-CT for non-thyroid purposes at our hospital between January 2016 and December 2020 were retrospectively reviewed, and 339 patients [185 men (mean age: 68 ± 11.2) and 154 women (mean age: 63 ± 15.0)] were found to have abnormal, either focal or diffuse, thyroid FDG uptake. After a thorough review of their medical records, US, and cytological/histological reports, 46 eligible patients with focal hypermetabolic TI were included in this study. The TIs were categorized as malignant and benign according to the cytological/histological reports, and four PET parameters [standardized uptake value (SUV)max, SUVpeak, SUVmean, and metabolic tumor volume (MTV)] were measured on FDG PET-CT. Total lesion glycolysis (TLG) was calculated by multiplying the SUVmean by MTV. Both parametric and non-parametric methods were used to compare the five parameters between malignant and benign lesions. Receiver operating characteristic (ROC) curve analysis was performed to identify a cut-off value.
RESULTS
Each of the 46 patients [12 men (26.1%; mean age: 62 ± 13.1 years) and 34 women (73.9%; mean age: 60 ± 12.0 years)] with focal hypermetabolic TIs had one focal hypermetabolic TI. Among them, 26 (56.5%) were malignant and 20 (43.5%) were benign. SUVmax, SUVpeak, SUVmean, and TLG were all higher in malignant lesions than benign ones, but the difference was statistically significant (P = 0.012) only for SUVmax. There was a positive linear correlation (r = 0.339) between SUVmax and the diagnosis of malignancy. ROC curve analysis for SUVmax revealed an area under the curve of 0.702 (P < 0.05, 95% confidence interval: 0.550-0.855) and SUVmax cut-off of 8.5 with a sensitivity of 0.615 and a specificity of 0.789.
CONCLUSION
More than half of focal hypermetabolic TIs on F-18 FDG PET-CT were revealed as malignant lesions, and SUVmax was the best parameter for discriminating between malignant and benign disease. Unexpected focal hypermetabolic TIs with the SUVmax above the cut-off value of 8.5 may have a greater than 70% chance of malignancy; therefore, further active assessment is required.
Core Tip: An unexpected focal thyroid incidentaloma (TI) is detected on various medical imaging studies. The lesion may harbor a risk of malignancy and the differentiation between malignant and benign disease is important. Standardized uptake value (SUV) is often measured for metabolism on F-18 fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET-CT). Parameters of FDG PET-CT, including SUV, have been studied for many years in the fields of nuclear medicine and oncology. We conducted the present study to distinguish malignant TI from benign disease with an analysis of FDG PET-CT parameters.
