18F-fluorodeoxyglucose positron emission tomography does not predict malignancy in thyroid nodules cytologically diagnosed as follicular neoplasm.
OBJECTIVE
The objective of this study was to evaluate the usefulness of (18)F-fluorodeoxyglucose positron emission tomography (FDG-PET) in predicting malignancy in thyroid nodules cytologically diagnosed as follicular neoplasm.


METHODS
A total of 46 patients with thyroid nodules larger than 1 cm in diameter cytologically diagnosed as follicular neoplasm at Asan Medical Center (Seoul, Korea) were included. FDG-PET images were taken in all patients before surgical resection, and the maximum standardized uptake value (SUVmax) of each nodule was measured.


RESULTS
FDG-PET showed hypermetabolic activity of all nodules compared with normal thyroid tissue. Thirty-six patients underwent surgery, whereas 10 refused immediate operation. Fifteen patients had cancer: 11 with follicular and two each with Hürthle cell and follicular variants of papillary cancer. Twenty-one patients had benign nodules: 11 follicular adenomas, eight adenomatous hyperplasias, and two Hürthle cell adenomas. SUVmax did not differ significantly between malignant and benign nodules (3.6 +/- 3.5 vs. 3.4 +/- 3.2; P = 0.83) or among subtypes of benign nodules (P = 0.23). However, SUVmax differed significantly among subtypes of malignant nodules (P = 0.02).


CONCLUSIONS
On FDG-PET, the glucose metabolic activities of benign thyroid follicular nodules were as high as those of malignant nodules. These findings suggest that FDG-PET has limited value for selecting candidates for surgery among patients cytologically diagnosed as follicular neoplasm.
Kim
Jung Min
JM
Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, 388-1 Pungnap-dong, Songpa-gu, Seoul 138-736, Korea.
Ryu
Jin-Sook
JS
Kim
Tae Yong
TY
Kim
Won Bae
WB
Kwon
Gui Young
GY
Gong
Gyungyub
G
Moon
Dae Hyuk
DH
Kim
Seong Chul
SC
Hong
Suck Joon
SJ
Shong
Young Kee
YK
D000236:Adenoma / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D018249:Adenoma, Oxyphilic / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D000328:Adult; D000368:Aged; D044963:Biopsy, Fine-Needle; D003937:Diagnosis, Differential; D005260:Female; D019788:Fluorodeoxyglucose F18; D005947:Glucose / Q000378:metabolism; D006801:Humans; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals; D016606:Thyroid Nodule / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery
D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; D005947:Glucose