The incidence of thyroid cancer in focal hypermetabolic thyroid lesions

Abstract

Background The clinical significance of incidental thyroid abnormalities discovered in 18F-FDG PET/CT (FDG PET/CT) studies remains controversial. The objective of this large retrospective study was to a) determine the prevalence of focal FDG thyroid uptake on whole body FDG PET/CT studies performed for non-thyroid cancers and b) to test whether intense focal FDG thyroid uptake is associated with malignancy. Methods A total of 11,921 FDG PET/CT studies in 6,216 patients performed at our institution between 01/2012 and 12/2014 were analyzed. We retrospectively reviewed the medical records of these patients. Eight hundred forty five/6,216 patients (13.6%) had a thyroid incidentaloma based on the clinical 18FDG PET/CT report. One hundred sixty/845 (18.9%) of these underwent ultrasound and 98 of these (61.3%) had a fine needle aspiration (FNA). Twenty-six of these 98 (26.5%) patients underwent thyroidectomy. Thyroid lesion and background SUV's for each patient were measured upon review of the 18FDG PET/CT study. We measured SUVmax, thyroid to background (1TLTBG), thyroid to blood pool (1TLBP) and thyroid to liver (1TLL) ratios in benign and malignant lesions. Receiver operating curves (ROC) were calculated to determine optimal cut off values between malignant and benign lesions Results Twenty-one of the 98 patients who underwent FNA biopsy or thyroidectomy had malignant disease (21.4%). Malignant lesions had significantly higher thyroid lesion SUVmax, 1TLTBG, 1TLBP, and 1TLL than benign nodules. The ROC derived cut off ratio 1TLTBG of >2.0 differentiated benign from malignant lesions best with a specificity and sensitivity of 0.76 and 0.88, respectively. Conclusions The incidence of malignancy in biopsied focal hypermetabolic thyroid lesions is 21.4%. Lesions on FDG PET/CT studies, exhibiting a ratio TLTBG>2.0, warrant further work up with ultrasound and FNA to exclude malignancy.

Thyroid Gland ¹⁸F-FDG Uptake in Neurofibromatosis Type 1

“…Our retrospective analysis of clinical records showed a comparable incidence of thyroid malignancy or other thyroid disease in NF1 patients compared to previous studies in non-thyroid cancer patients [24-27]. Only one study by Ferner et al [7] described a case of FDG-PET-positive thyroid cancer in a population of NF1 patients ( n = 105; 1%) discovered through PET/CT.…”

“…Demir et al [24], Bae et al [25], and Adas et al [26] showed lower percentages in non-thyroid cancer patients with a range between 1 and 3%. However, the most recent study with the largest population by Barrio et al [27] reported a comparable percentage of focal incidentaloma compared to this study (13.6%). Karantanis et al [28] reported a diffuse increased uptake in 2.9% of 4,732 non-thyroid cancer patients, which is comparable to our results.…”

Diagnostic Value of Volume-Based Fluorine-18-Fluorodeoxyglucose PET/CT Parameters for Characterizing Thyroid Incidentaloma

“…Dual-time-point 18 F-FDG PET/CT and retention index were used in differential diagnosis of thyroid incidentaloma ( 28 ). Barrio et al ( 29 ) measured SUVmax, thyroid to background thyroid lesion SUVmax/thyroid background SUVmean (TL/TBG), thyroid to blood pool TL/blood pool SUVmean (BP), and thyroid to liver TL/liver SUVmean (L) ratios in benign and malignant lesions to test if intense focal 18 F-FDG thyroid uptake is associated with malignancy. These studies revealed various methods may significantly improve accuracy of PET/CT for differentiating benign from malignant focal thyroid lesions.…”

18F-FDG PET/CT imaging of atypical subacute thyroiditis in thyrotoxicosis

“…It is not only caused by malignancy, but also by a variety of benign lesions such as nodular hyperplasia, Hurthle cell and follicular neoplasms, and even chronic lymphocytic thyroiditis. Barrio et al [ 16 ] demonstrated that 845/6212 (13.6%) patients with nonthyroid cancers had a thyroid incidentaloma, and 21 of the 98 patients who underwent fine-needle aspiration biopsy or thyroidectomy had malignant disease (21.4%), whereas the others (78.6%) had benign tumors. Increased FDG uptake in skeletal muscle and decreased uptake in the liver are also observed in a variety of pathological and physiological conditions.…”