Prevalence and Characteristics of Incidentalomas Discovered by Whole Body FDG PETCT

Abstract

Objectives. To determine the prevalence of incidentalomas in a patient population with no known thyroid malignancy who underwent whole body FDG-PET/CT for staging or restaging of neoplasia. The additional aim of the study was to evaluate the feasibility of using PETCT as a screening tool for malignant thyroid incidentalomas. Methods. Retrospective review of medical records of all the thyroid exams done at our institution between January 1, 2000 and August 20, 2008. We made a criterion of PET/CT as the primary method of detection of incidentalomas. Results. From a total of 8464 thyroid exams, 156 incidentalomas were found and 40 incidentalomas underwent anatomopathology analysis, which was used as gold standard. Chi-square analysis was used to analyze the data. There is no significant association between SUV value and the prevalence of incidentalomas. Discussion. From January 1, 2000 to August 20, 2008, incidentalomas have a prevalence of 1.84% at our institution. 38% of the incidentalomas that were biopsied were characterized as representing malignant tumors. Conclusion. Focal, abnormal FDG uptake representing incidentalomas must be followed up with biopsies. It is impractical to use PET/CT as a screening tool to detect incidentalomas for the general population but it must be done in patients with history of any type of cancer.

Incidence and Significance of Incidental Focal Thyroid Uptake on ¹⁸F-FDG PET Study in a Large Patient Cohort: Retrospective Single-Centre Experience in the United Kingdom

“…The significance of incidental focal thyroid uptake on 18 F-FDG PET study was first described in 2001 [10]. Many research studies are currently available on this topic, with different results on focal uptake of tracer on 18 F-FDG PET [3,4,5,6,8,9,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38]; however, a large UK series has yet to be reported. We report one of the largest studies on the evaluation of incidental focal 18 F-FDG uptake in the thyroid.…”

“…Literature evidenceon the SUV max in benign and malignant lesions vary with several reports showing a statistically significant difference [9,13,19,21,22,23,34,41] whilst many others have shown no significant difference [8,14,15,27,30,32,33,35,36]. Previous studies have also reported cutoff SUV values ranging from 3.5 to 5 in differentiated benign to malignant thyroid lesions [24,34,41].…”

Cytological evaluation by fine needle aspiration biopsy of incidental focal increased fluorodeoxyglucose uptake in thyroid on positron emission tomography scan

“…It is also utilized for cancer screening. 4 Diffuse type generally suggests a benign lesion since most cases are autoimmune thyroiditis, 5,6 with rare exceptions. 2 With the ever increasing use of FDG-PET in oncology, the reported incidence of PET-avid incidentalomas ranges between 0.2% and 8.9%.…”

“…A diffuse type means increased FDG uptake in the whole thyroid gland, whereas with the focal type the area of increased uptake is limited to less than one lobe. 4 Diffuse type generally suggests a benign lesion since most cases are autoimmune thyroiditis, 5,6 with rare exceptions. However, focal FDG uptake carries certain risk of thyroid malignancy.…”

“…Almost half of the studies claimed that higher SUVmax was correlated with thyroid cancer, 14,15,19,20 while the other half reported no significant difference between benign and malignant SUVmax. 4,16,21,22 This study aims to evaluate the clinical significance of focal thyroid FDG uptake and establish the prevalence of malignancies as well as benign lesions in our tertiary medical center. The potential diagnostic value of SUVmax values was also assessed.…”