A 70-year-old man with history of hypertension, diabetes and chronic
kidney disease was diagnosed with an early stage right papillary thyroid
carcinoma in 1999.
This was initially treated by total thyroidectomy and radioactive iodine
ablation with pathology indicating extrathyroidal extension into skeletal
muscle and one parathyroid gland. He had a local recurrence in 2003 when he was
found to have a subcutaneous nodule at the side of incision. This was excised
locally along with a right modified radical neck dissection followed by another
dose of radioactive iodine.
demonstrates distortion along the glottic region by presumed post-operative
changes. The red circle denotes a submental lymph node, which was
Images courtesy of M. Gehsani, MD
PET/CT examination again demonstrates distortion of the glottic region and
increased soft tissue with corresponding mild hypermetabolic activity with a
maximal standard uptake value of 2.4. Note resolution of the previously seen
submental lymph node.
He had been continuing on thyroid-stimulating hormone suppressive
therapy with thyroxine and had regular follow-up exams. However, he had
multiple local recurrences requiring surgical resection, including partial
laryngeal resection and tracheotomy. He underwent a FDG-PET/CT scan in 2010
that was concerning for distant metastases. There was increased fullness in the
soft tissues within the thyroid bed without any discrete mass on the CT
portion. There was fullness of the pretracheal soft tissues inferior to the
tracheostomy stoma demonstrating a low grade metabolic activity with a maximum
standard uptake value of 2.4. However, there was a new hypermetabolic lytic
lesion along the left iliac bone with standard uptake value of 8.3, consistent
with skeletal metastases.
This image demonstrates clips along the thyroidectomy bed.
There was no evidence of recurrence at the time.
PET/CT demonstrates placement of a tracheostomy tube. The thyroidectomy bed
demonstrates mild hypermetabolic activity with a maximal standard uptake value
The remarkable difference between low grade diffuse metabolic activity
in the local treatment bed as opposed to the well-defined round focus of
intense hypermetabolic activity in the distant metastases makes it more likely
that the former is due to post-therapy changes rather than local/regional
recurrence. Currently, the patient is being evaluated for further management of
his distant metastatic disease.
This image is
representative of the osseous structures failing to demonstrate osseous
follow-up PET/CT, a new lytic lesion is seen along the left iliac bone with
corresponding intense hypermetabolic activity with a maximal standard uptake
value of 8.3. Due to this distant metastasis showing intense FDG uptake, it is
presumed that the mild hypermetabolic activity along the thyroidectomy bed and
glottic region is post-operative and not indicative of local
The incidence of thyroid cancer has been increasing in the past decade.
This is partly due to the earlier detection of subclinical disease by
ultrasonography and biopsy of the thyroid nodules. The treatment of
differentiated papillary and follicular thyroid cancers includes combination of
surgery, radioiodine ablation and thyroid hormone suppression. The prognosis is
generally excellent with 5-year survival about 90% in patients without
metastatic disease. Prognostic factors related to cancer recurrence and
mortality include age, size of the primary tumor, soft tissue invasion and
Robbins and colleagues showed the importance of FDG-PET as a prognostic
tool in patients with metastatic disease. Patients who had a positive FDG scan
were more likely to have increased cancer-related mortality compared with
patients with negative FDG scans. Also, the patients with only locally positive
FDG activity had a better survival than those with distant sites of FDG
activity. Thus, the role of FDG-PET scanning in thyroid cancer has been
increasing from localization imaging to providing important prognostic
The PET scans are especially useful in patients with negative
radioiodine uptake and both of these imaging modalities complement each other
to evaluate distant metastatic disease. The well-differentiated cancers can
become less differentiated and fail to take up iodine, making the radioiodine
scans less sensitive. However, these less differentiated cancers may have an
increased metabolic activity and a high FDG uptake, resulting in improved
sensitivity of FDG-PET scanning.
Recent meta-analysis by Dong and colleagues showed that the pooled
sensitivity and specificity of FDG-PET scan in patients with elevated
thyroglobulin levels and a negative radioiodine scan was 88.5% and 84.7%,
respectively. The long-term follow-up of these patients usually includes
clinical examinations, serum thyroglobulin levels and neck imaging using
ultrasonography. In patients with a clinical suspicion of recurrence,
additional imaging including radioiodine scan and FDG-PET/CT scans can be used
to identify the sites of metastases.
Sumit Talwar, MD, is hematology oncology fellow at St
Lukes-Roosevelt Hospital Center.
Neil Gupta, MD, is a resident in radiology at St
Lukes-Roosevelt Hospital Center.
Daniel B. Kuriloff, MD, FACS, is director of the Center for Thyroid
and Parathyroid Surgery, The New York Head and Neck Institute, and associate
clinical professor, Otolaryngology-Head and Neck Surgery, at Columbia
University College of Physicians and Surgeons.
Munir Ghesani, MD, is an attending radiologist at St.
Lukes-Roosevelt Hospital Center and associate clinical professor of
radiology at Columbia University College of Physicians and Surgeons.
For more information:
- Dong MJ. Nucl Med Commun. 2009;30:639-650.
- Robbins RJ. J Clin Endocrinol Metab.