Case Author(s): David A. Hillier, M.D., Ph.D. and Barry A. Siegel, M.D. , . Rating: #D2, #Q3

Diagnosis: Papillary carcinoma of the thyroid

Brief history:

74-year-old man with a right lower lobe solitary pulmonary nodule.


PET images

View main image(pt) in a separate image viewer

View second image(us). Thyroid ultrasonography.

Full history/Diagnosis is available below

Diagnosis: Papillary carcinoma of the thyroid

Full history:

74-year-old man with an enlarging solitary pulmonary nodule in the right lower lobe.


15.0 mCi fluorodeoxyglucose (FDG), IV


FDG-PET images (anterior projection image and coronal, axial, and sagittal images at the level of the thyroid gland show a focus of intense FDG uptake in the region of the left lobe of thyroid. The right lung nodule is not shown on these images, but had only moderate FDG uptake, with a standardized uptake value (SUV) of 1.7 (benign range)

Thyroid ultrasonography obtained following the PET study shows a 1.0 x 1.0 x 1.2 cm hypoechoic nodule in the inferior aspect of left thyroid lobe, correlating with the abnormality seen on FDG-PET.


The probability of thyroid cancer in a focal thyroid abnormality found incidentally on FDG-PET has not been defined, but one preliminary report suggests that the risk is about 50%. Diffuse thyroidal uptake of FDG is most likely due to Hashimoto's thyroiditis.

The role of FDG-PET in thyroid carcinoma is unclear. Some have suggested it may find use in distinguishing follicular adenoma from follicular carcinoma (a difficult distinction to make with small tissue samples). I-123 imaging has been used for this purpose (normal or high uptake suggesting adenoma and low uptake suggesting tumor).

Several investigators report results indicating that FDG-PET may be useful for imaging and staging anaplastic thyroid tumors. Well-differentiated thyroid tumors that take up I-131 well commonly do not take up FDG well (95% per Feine, et al), while tumors that do not take up I-131 well appear to have high glucose metabolism and good FDG uptake.


Feine, U, et al. Fluorine-18-FDG and Iodine-131-Iodide uptake in thyroid cancer. J Nucl Med. 37, 1468-1471. 1996.

Gasparoni P. Potential role of fluorine-18-deoxyglucose (FDG) positron emission tomography (PET) in the staging of primitive and recurrent medullary thyroid carcinoma. J Endocrinol Invest. 20, 527-530. 1997.

Grünwald F, et al. Comparison of 18-FDG-PET with 131-iodide and 99m-Tc-sestamibi scintigraphy in differentiated thyroid cancer. Thyroid. 7, 327-335. 1997.

Rigo P, et al. Oncological applications of positron emission tomography with fluorine-18 fluorodeoxyglucose. Eur J Nucl Med. 23, 1641-1674. 1996.


Thyroid fine-needle aspiration 6/24/98 revealed papillary carcinoma

Thyroidectomy was performed on 7/6/98, revealing papillary thyroid carcinoma, classical type. There was extension into the perithyroidal fat. Surgical margins were clear. One perithyroidal lymph nodes was positive for tumor. The patient subsequently underwent ablation of residual functioning thyroid tisse with I-131.

Two months later, CT of chest showed that the right lower lobe nodule was slowly enlarging and thus was suspicious for bronchogenic carcinoma. The nodule was resected on 8/10/98, revealing a necrotizing granuloma, with no evidence of acid-fast bacilli.

ACR Codes and Keywords:

References and General Discussion of PET Tumor Imaging Studies (Anatomic field:Face, Mastoids, and Neck, Category:Neoplasm, Neoplastic-like condition)

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Case number: pt025

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