The Characteristics and Significances of Incidental Focal Uptake by PET-CT in the Thyroid Gland

Kim, Ju Yeon; Moon, Hyung Gon; Jung, Eun Jung; Jeong, Tae Sik; Jeong, Soon Il; Jeong, Sang Ho; Jeong, Chi Young; Ju, Young Tae; Lee, Young Joon; Hong, Soon Chan; Choi, Sang Kyung; Ha, Woo Song; Park, Soon Tae

Abstract

PURPOSE
The increased use of positron emission tomography-computed tomography (PET-CT) has resulted in increased detection of incidentally found thyroid lesions. The purpose of this study was to determine the clinical significance of incidental PET-CT uptake in the thyroid and the characteristics of malignant thyroid lesions.
METHODS
A retrospective review was conducted on the patients who were incidentally found to have abnormal uptake of thyroid on PET-CT. The patients' records were assessed for the demographics, the PET-CT findings, the standard uptake values (SUVmax), the ultrasonography findings, the fine needle aspiration (FNA) cytology and the surgical pathologic findings.
RESULTS
One hundred-ten (4.0%) individuals were identified to have focal (n=35) or diffuse (n=75) thyroid uptake. Thyroid ultrasonography was performed on 29 patients with 35 focal thyroid uptakes, and there was no correlation between the mass size on ultrasonography and the SUVmax on PET-CT. The cytologic diagnosis was available for 26 patients and in 16 (61.53%) patients, the nodule was found to be malignant. The mean and standard deviation of the SUVmax was 5.21±4.08 for the malignant nodules and 8.78±7.32 for the benign nodules. There was no significant difference in the SUVmax between the benign and malignant nodules.
CONCLUSION
In our study, focal thyroid uptakes incidentally found on PET-CT had a high risk of thyroid malignancy (55.17%). There seems to be no correlation between the SUVmax of the lesion and the risk of malignancy.