Chronic thyroiditis: diffuse uptake of FDG at PET.

Abstract

Diffuse thyroidal FDG uptake may be an indicator of chronic thyroiditis. The actual prevalence of the disorder was not low in this series, and such lesions may be found incidentally at FDG PET.

The Significance and Management of Incidental [18F]Fluorodeoxyglucose–Positron-Emission Tomography Uptake in the Thyroid Gland in Patients with Cancer

“…Although diffuse thyroid uptake in FDG-PET is believed to be either a normal variant, chronic thyroiditis, or Graves disease, focal thyroid lesions have been associated with a high risk for malignant tumors. [1][2][3][4][5][6][7][8][9][10] Unfortunately, no definitive studies have identified specific characteristics that increase the likelihood of a malignant tumor. Although standard uptake values (SUV max ) has been introduced to predict malignant potential, investigators are still divided regarding this issue.…”

Clinical Significance of Diffuse 18F-FDG Uptake in Residual Thyroid Gland after Unilateral Thyroid Lobectomy

“…A 1.8% prevalence of diffuse thyroid uptake was reported by Chen et al [9]. Yasuda et al demonstrated diffuse 18 F-FDG uptake in the thyroid in 36 of 1,102 healthy subjects (3.3%) [10]. These results showed relatively similar incidence of diffuse thyroid uptake in the healthy subjects and cancer patients.…”

“…In inflammatory conditions, the thyroid gland shows low attenuation on CT because of follicular cell destruction and loss of iodine concentration [14,18,19]. Thus, data regarding TgAb elevation, ultrasonography, and low attenuation value of CT revealed that chronic thyroiditis was suggested in 95.2% of the diffuse uptake group, and this percentage is similar to the 94.4% found by Yasuda et al [10]. Therefore, a possible explanation for diffuse uptake in the residual thyroid is mostly associated with chronic thyroiditis in the present study.…”

“…Interestingly, Tateish et al recently found that 20% of breast cancer patients in their study population showed diffuse thyroid uptake in PET/CT, which was significantly greater compared to the results of previous studies [14]. Although the precise mechanism for diffuse thyroid uptake is still unknown, the possibility of lymphocytic infiltration or active fibrosis formation related to chronic thyroiditis has been suggested [10,11]. 18 F-FDG PET is a noninvasive whole body imaging technique used to evaluate many kinds of malignant tumors.…”

“…A thyroid lesion with focal 18 F-FDG uptake is likely to be malignant [5][6][7][8][9], whereas diffusely increased uptake in the thyroid gland is associated with several thyroid disorders including chronic thyroiditis, Graves' disease, and diffuse goiter [9][10][11][12][13]. Several studies have reported that incidence of diffusely increased 18 F-FDG uptake in the thyroid gland was 0.6-3.3%.…”