Korean J Endocr Surg.  2016 Mar;16(1):18-23. 10.16956/kaes.2016.16.1.18.

Papillary Thyroid Carcinoma with Retropharyngeal Node Metastasis Demonstrating Negative I-131 but Positive FDG Uptake on PET/CT

• Son H
• Hong HJ
• Ryu J
• Lee JW
• Yoon RG
• Lee I

• KMID: 2158624
• DOI: http://doi.org/10.16956/kaes.2016.16.1.18

Abstract

Papillary thyroid carcinoma (PTC) is commonly accompanied by cervical lymph node metastasis, whereas metastases to the retropharyngeal lymph nodes (RPN) are rare. Radioactive iodine (RAI) ablation is recommended for detection and treatment of differentiated thyroid carcinoma (DTC). However, in some cases of iodine-negative DTC, F-18 fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) can aid in detection of additional lesions. We report on a patient with PTC who had retropharyngeal node involvement with iodine-negative features and low thyroglobulin level at the time of diagnosis but with metastasis identified on FDG PET/CT.

Keyword

Papillary thyroid cancer; Retropharyngeal lymph node; 18F-FDG PET/CT; Radioiodine scan

MeSH Terms

Diagnosis
Electrons
Humans
Iodine
Lymph Nodes
Neoplasm Metastasis*
Positron-Emission Tomography and Computed Tomography*
Thyroglobulin
Thyroid Gland*
Thyroid Neoplasms*
Iodine
Thyroglobulin

Figure

• 

  Fig. 1 Images of preoperative CT showing multiple neck lymph node metastases. Contrast-enhanced CT images showing multiple hyper-enhancing lymph nodes in the left retropharyngeal space and left neck at level 2 (A), level 3 (B), and level 4 (C). On contrast-enhanced CT images obtained one year after surgery, enlarged, enhancing lymph nodes remain in the left retropharyngeal space and left neck level 2 (D). The sizes of the residual contrast-enhancing lymph nodes did not significantly change during the follow-up period.

• 

  Fig. 2 Anterior and posterior images of the post-ablative I-131 scan. Three months after total thyroidectomy, the patient underwent I-131 ablation with a dose of 5.55 GBq. Post-ablative scanning performed three days after I-131 administration shows a focus of increased I-131 uptake in the thyroid bed, suggesting remnant thyroid uptake. With the exception of remnant thyroid uptake, no other abnormal I-131 uptake suggesting thyroid cancer metastasis is seen.

• 

  Fig. 3 (A) Two enlarged lymph nodes with increased FDG uptake were noted in the left neck level II (SUVmax of 11.1) and retropharyngeal space (SUVmax of 17.6) on fused trans-axial FDG PET/CT images. (B) Retropharyngeal and level IIb lymph node involvement was verified as metastatic papillary thyroid carcinoma.

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