Elsevier

Surgery

Volume 130, Issue 6, December 2001, Pages 941-946
Surgery

American Association of Endocrine Surgeons
Risk of malignancy in thyroid incidentalomas identified by fluorodeoxyglucose-positron emission tomography*

Presented at the 22nd Annual Meeting of the American Association of Endocrine Surgeons, Atlanta, Ga, April 28-May 1, 2001.
https://doi.org/10.1067/msy.2001.118265Get rights and content

Abstract

Background. Thyroid tumors often exhibit increased metabolic activity, as evidenced by enhanced glucose uptake on positron emission tomography (PET) with use of 18F-fluorodeoxyglucose (FDG). The incidence of new thyroid lesions found on routine FDG-PET has not been previously reported. Methods. A retrospective review of all patients who underwent FDG-PET imaging at our institution from June 1, 1996, through March 15, 2001, identified patients with a newly diagnosed thyroid lesion. Thyroid incidentaloma was defined as a thyroid lesion seen initially on FDG-PET in a patient without a history of thyroid disease. Available follow-up data were documented. Results. One hundred and two of 4525 FDG-PET examinations (2.3%) demonstrated thyroid incidentalomas. Eighty-seven of 102 patients had no thyroid histology because of other malignancies. Fifteen patients had thyroid biopsy: 7 (47%) with thyroid cancer, 6 (40%) with nodular hyperplasia, 1 with thyroiditis, and 1 with atypical cells of indeterminate origin. The average standardized uptake values were higher for malignant compared with benign lesions. Conclusions. Thyroid incidentaloma identified by FDG-PET occurred with a frequency of 2.3%. Of the thyroid incidentalomas that underwent biopsy, 47% were found to be malignant. Given the risk of malignancy, patients with new thyroid lesions on PET scan should have a tissue diagnosis if it will influence outcome and management. Standardized uptake values may be helpful in predicting benign versus malignant histology. (Surgery 2001;130:941-6.)

Section snippets

Patient selection

Records of all patients who underwent clinical FDG-PET studies at our institution between June 1, 1996, and March 15, 2001, were reviewed. This group of patients (n = 4525) was then narrowed to include only patients whose FDG-PET examinations identified an unsuspected thyroid abnormality. A thyroid incidentaloma was defined as a new focal or diffuse thyroid abnormality identified for the first time on FDG-PET examination in a patient without prior history of thyroid disease. Records of the

Results

Of the 4525 FDG-PET examinations reviewed from June 1, 1996, to March 15, 2001, 102 patients (2.3%) met criteria for having a thyroid incidentaloma. Demographics on these 102 patients included 60 women, 42 men, an age range of 32 to 87 years (mean age, 64.5 ± 12.0 years), and no prior history of thyroid disease. Of the 102 patients who had a thyroid incidentaloma on FDG-PET, 71 had a focal area of increased FDG uptake (localized to the left lobe in 36 patients and to the right lobe in 35

Discussion

Since thyroid nodules are relatively common, with a prevalence of anywhere from 4% to 7%, it is important to be able to identify which nodules are at risk for containing malignancy. This holds true for thyroid nodules discovered incidentally on other examinations. In our study, thyroid incidentaloma seen on FDG-PET occurred with an incidence of 2.3%. Although the incidence of thyroid malignancy in the general population is much lower, averaging about 0.004% to 0.1% per year, the risk of finding

Discussion

Dr Steven Libutti (Bethesda, Md). I enjoyed your paper very much. As PET is becoming a much more common imaging modality, more and more of these incidentalomas are going to be cropping up information on what to do about them is very important.

My question actually is a bit of a twist on what your paper was about. Given the use of standard uptake values and seeing that you can distinguish malignant lesions in the thyroid from benign lesions in the thyroid based on their SUV, do you think this

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*

Reprint requests: Jeffrey F. Moley, MD, Washington University School of Medicine, Department of Surgery, Box No. 8109, 660 S Euclid Ave, St Louis, MO 63110.

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