The dilemma of 18F-FDG PET/CT thyroid incidentaloma: what we should expect from FNA. A systematic review and meta-analysis

Abstract

Purpose 18F-FDG thyroid incidentaloma (TI) occurs in ~2% of PET/CT examinations with a cancer prevalence of up to 35–40%. Guidelines recommend fine-needle aspiration cytology (FNA) if a focal 18F-FDG TI corresponds to a sonographic nodule >1 cm. The aim of this systematic review and meta-analysis was to provide evidence-based data on the diagnostic distribution of 18F-FDG TIs in the six Bethesda systems for reporting thyroid cytopathology (BETHESDA) subcategories. Methods Original studies reporting 18F-FDG TIs and cytologically classified according to BETHESDA were included. Six separate meta-analyses were performed to obtain the pooled prevalence (95% confidence interval, 95% CI) of 18F-FDG TIs in the six BETHESDA subcategories. Results Fifteen studies were finally included. Nine studies were from Asian/Eastern and six from Western countries. FNA data according to BETHESDA was available in 2304 cases. The pooled prevalence of 18F-FDG TIs according to BETHESDA was BETHESDA I 10% (6–14), BETHESDA II 45% (37–53), BETHESDA III 8% (3–13), BETHESDA IV 8% (5–12), BETHESDA V 6% (4–9), BETHESDA VI 19% (13–25). A significantly different prevalence was found in the BETHESDA IV between Asian/Eastern (2%) and Western (19%) studies. Conclusion Two-thirds of focal 18F-FDG TIs undergoing FNA have either malignant (BETHESDA VI) or benign (BETHESDA II) cytology while a minority will have indeterminate (BETHESDA III or IV) FNA results. Significant differences between Asian/Eastern and Western studies are also present in the prevalence of indeterminate FNA results.

The co-occurrence of both breast- and differentiated thyroid cancer: incidence, association and clinical implications for daily practice

“…Fluorodeoxyglucose-positron emission tomography/computed tomography also called a FDG-PET/CT scan was found to be useful in the first 5 years of follow-up of BC patients with BRCA1/2 mutations [ 28 ]. In 2% of PET/CT examinations, FDG-thyroid incidentaloma are detected with a thyroid cancer prevalence of 35–40% [ 29 ]. These incidental findings may explain the increased TC incidence during the first 5 years of BC follow-up in our study.…”

Artificial Intelligence in Thyroid Field—A Comprehensive Review

“…Further improvement of US performance by AI remains however desirable [ 77 , 78 ]. In addition, a not negligible number of thyroid goiters are incidentally discovered during other imaging evaluations (i.e., CT, MR, PET/CT) of patients with non-thyroid indication [ 79 ]. While the performance of these imaging procedures is poor or suboptimal to identify malignant and benign nodules among adrenal thyroid incidentalomas, a significant effort should be made in the future to improve their capability to initially select patients requiring an urgent or not endocrinological evaluation combined with in-office US examination.…”

Radiomics Analysis of [18F]FDG PET/CT Thyroid Incidentalomas: How Can It Improve Patients’ Clinical Management? A Systematic Review from the Literature

“…Thyroid incidentaloma (TI) is defined as a thyroid gland lesion incidentally and newly discovered during non-thyroid related imagistic examinations, such as ultrasound, conventional radiology, and nuclear medicine investigations, performed for unrelated and non-thyroid purposes [ 1 , 2 ]. Incidentally discovered [ 18 F]-Fluorodeoxyglucose (FDG)-avid thyroid lesions have been reported in about 1.2–4.3% [ 2 , 3 , 4 , 5 , 6 , 7 ]; between 14–63.3% have been confirmed as malignant [ 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 ], with some authors stating that the malignancy rate could reach up to 80% [ 7 ]. However, the great statistical heterogeneity between studies must be taken into consideration [ 2 , 9 , 10 ].…”