Positron emission tomography occasionally
reveals incidental thyroid nodules
(November 2003)
The background of the study. 18F-Fluorodeoxglucose
(FDG) positron emission tomography is being used to detect metastases
in patients with cancer, and also to screen for cancer in healthy
people. Like other imaging procedures, FDG imaging may reveal unsuspected
thyroid nodules (incidentalomas). In this study, the frequency of
detection of thyroid nodules and the nature of those nodules were
studied in patients undergoing FDG imaging for possible nonthyroid
tumors.
How the study was done. The study
subjects were 1330 consecutive patients who underwent imaging with
FDG at a cancer center. In 999 patients the imaging test was done
during an evaluation for metastatic cancer, and in 331 patients
it was done as a screening test for cancer. Patients with thyroid
cancer were excluded. Thyroid incidentaloma was defined as focal
or diffuse uptake in the thyroid region; focal uptake was uptake
in less than one thyroid lobe, and diffuse uptake was uptake throughout
both thyroid lobes.
The results of the study. Thyroid
incidentaloma occurred in 29 patients (2 percent), 21 of whom had
focal uptake and 8 diffuse uptake. In 15 of the 21 patients who
had focal thyroid uptake of FDG, the nodule was biopsied or removed
surgically. Four patients proved to have a papillary thyroid carcinoma,
four had a follicular adenoma, and seven had a hyperplastic nodule;
the other six patients were not further studied. Among the eight
patients with diffuse thyroid uptake of FDG, seven had chronic thyroiditis
and one had subacute granulomatous thyroiditis.
The conclusions of the study. Positron
emission tomography using 18F-fluorodeoxyglucose, like
other imaging tests, may reveal incidental thyroid abnormalities,
including thyroid carcinomas.
The original article. Kang KW, Kim
SK, Kang HS, Lee ES, Sim JS, Lee IG, Jeong SY, Kim SW. Prevalence
and risk of cancer of focal thyroid incidentaloma identified by
18F-fluorodeoxyglucose positron emission tomography for
metastasis evaluation and cancer screening in healthy subjects.
J Clin Endocrinol Metab 2003;88:4100-4.
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