J Breast Cancer.  2009 Dec;12(4):309-315. 10.4048/jbc.2009.12.4.309.

The Clinical Significance of Diffuse Thyroid Uptake That is Incidentally Identified by F-18 FDG PET/CT Imaging in Patients with Breast Cancer

• Jeong YJ
• Lim ST
• Kim DW
• Jeong HJ
• Youn HJ
• Jung SH
• Sohn MH

• KMID: 2175530
• DOI: http://doi.org/10.4048/jbc.2009.12.4.309

Abstract

PURPOSE
This study was to investigate the clinical significance of diffusely increased F-18 FDG uptake in the thyroid gland as an incidental finding on F-18 FDG PET/CT imaging in patients with breast carcinoma. METHODS: One hundred four patients with breast carcinoma who had no prior history of thyroid disease were enrolled. All patients underwent F-18 FDG PET/CT, ultrasound and thyroid function test (TFT-TSH, FT4, and T3), anti-TPO antibody test within 2 weeks. Also we checked estrogen (ER) and progesterone receptors (PR). We classified all patients into subgroups according to the existence and degree of F-18 FDG uptake in the thyroid gland, and evaluated the difference between subgroups. RESULTS: Of the 104 patients, 42 (40.4%) subjects showed diffusely increased thyroid uptakes. There was no significant difference in rate of abnormality in TFT and thyroid US, and existence of anti-TPO antibody and ER/PR between two groups. Of 42 patient who showed diffuse uptake, 12 (28.5%), 13 (31.0%), and 17 (40.5%) subjects demonstrated hypointense, isointense, and hyperintense thyroid uptake compared with activity of mediastinal blood pool. Thirteen (76.4%) of 17 subjects in the hyperintense thyroid uptake group revealed abnormality in various tests (US, TFT, and anti-TPO antibody). The rate of abnormality in this group was significantly different with the other two groups (p=0.002). CONCLUSION: Our data suggested that the rate of diffuse thyroid uptakes on F-18 FDG PET/CT imaging of patients with breast carcinoma was higher than healthy subjects. In case of someone who had no prior thyroid disease showed diffuse thyroid uptakes more than activity of mediastinal blood pool on F-18 FDG PET/CT imaging, it should be considered further evaluation about the thyroid gland.

Keyword

Breast; Carcinoma; Diffuse; F-18 FDG PET/CT; Thyroid

MeSH Terms

Breast
Breast Neoplasms
Estrogens
Humans
Incidental Findings
Receptors, Progesterone
Thyroid Diseases
Thyroid Function Tests
Thyroid Gland
Estrogens
Receptors, Progesterone

Figure

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  Figure 1 A case of diffusely increased F-18 FDG uptake, but less than activity of mediastinal blood pool, in the thyroid gland of 55-yr-old patient. On ultrasound examination, echogenecity of thyroid gland was homogeneous and blood flow was normal. Serum TSH was 2.61 mIU/L (reference range, 0.17-4.05 mIU/L), free T4 was 10.9 ng/dL (reference range, 9.4-25 ng/dL) and T3 was 2.03 ng/dL (reference range, 0.8-2.2 ng/dL), suggestive of normal state of thyroid function. Shown are 3D MIP image (A), transaxial PET image (B), transaxial fused PET/CT image (C), ultrasound image (D), and doppler ultrasound image (E).

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  Figure 2 A case of diffusely increased F-18 FDG uptake, similar intensity with mediastinal blood pool, in the thyroid gland of 46-yr-old patient. On ultrasound examination, thyroid gland was homogeneous and blood flow was mildly increased. Serum TSH was 2.09 mIU/L, free T4 was 11.3 ng/dL and T3 was 1.22 ng/dL, suggestive of normal state of thyroid function.

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  Figure 3 A case of intensely and diffusely increased F-18 FDG uptake, more than activity of mediastinal blood pool, in the thyroid gland of 58-yr-old patient. On ultrasound examination, thyroid gland was prominent and heterogeneous. Blood flow of thyroid gland was slightly increased. Serum TSH was 2.09 mIU/L, free T4 was 11.3 ng/dL, T3 was 1.22 ng/dL and TPO antibodies were elevated at 100 IU/mL (reference range, 0-0.3 IU/mL), suggestive of diagnosis of Hashimoto's thyroiditis.

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