World Journal of Nuclear Medicine

CASE REPORT
Year
: 2021  |  Volume : 20  |  Issue : 3  |  Page : 312--315

Follicular thyroid carcinoma metastasizing to rare sites and exhibiting variable inter-lesional heterogeneity on 18F-fluorodeoxyglucose positron emission tomography/computed tomography and 131I


Rahul V Parghane, Sandip Basu 
 Radiation Medicine Centre, Bhabha Atomic Research Centre, Tata Memorial Hospital Annexe; Homi Bhabha National Institute, Mumbai, Maharashtra, India

Correspondence Address:
Dr. Sandip Basu
Radiation Medicine Centre, Bhabha Atomic Research Centre, Tata Memorial Hospital Annexe, Jerbai Wadia Road, Parel, Mumbai - 400 012, Maharashtra
India

Abstract

A patient of differentiated follicular thyroid carcinoma with unusual sites of metastases is illustrated with 131I and 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) imaging findings. The described case harbored extremely rare metastasis to the urinary bladder with multi-organ metastatic disease (including unusual sites of right bronchus and hepatic metastases). There was inter-lesional heterogeneity among the metastatic lesions with regard to the 131I and FDG uptake in the aforementioned lesions. The detection of such heterogeneity has important implications for patient management in metastatic differentiated thyroid carcinoma.



How to cite this article:
Parghane RV, Basu S. Follicular thyroid carcinoma metastasizing to rare sites and exhibiting variable inter-lesional heterogeneity on 18F-fluorodeoxyglucose positron emission tomography/computed tomography and 131I.World J Nucl Med 2021;20:312-315


How to cite this URL:
Parghane RV, Basu S. Follicular thyroid carcinoma metastasizing to rare sites and exhibiting variable inter-lesional heterogeneity on 18F-fluorodeoxyglucose positron emission tomography/computed tomography and 131I. World J Nucl Med [serial online] 2021 [cited 2021 Oct 16 ];20:312-315
Available from: http://www.wjnm.org/text.asp?2021/20/3/312/294669


Full Text

 Introduction



The cervical lymph node is the most common organ for metastasis in differentiated thyroid carcinoma (DTC). At the same time, lungs, bones, and at times, the brain are the usual organs for distant metastases in DTC. Metastasis to the urinary bladder in DTC is extremely rare for distant organ involvement. To the best of our knowledge, only four such cases have been reported in the literature.[1],[2],[3],[4] 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) scan has a valuable complementary role in the evaluation of thyroid carcinoma,[5],[6] while 131I as theranostic agent (used for both purposes of imaging and therapy) remains the cornerstone in the management of DTC.[7] The interesting feature of our case was extremely rare metastasis to the urinary bladder with multi-organ metastatic disease (including unusual sites of the right bronchus and hepatic metastases) and the observation of inter-lesional heterogeneity on molecular imaging which may guide therapeutic management and follow-up in this case with rare site metastatic disease.

 Case Report



A 54-year-old male patient presented with cough and occasional hemoptysis for 1 year and hematuria for 6 months. The contrast-enhanced computed tomography (CECT) was used for the evaluation of these complaints. CECT of the thoracic region [Figure 1]a demonstrated soft-tissue mass lesions in the hilar region of the right lung. CECT scan of the pelvic region [Figure 1]b showed soft-tissue lesion in the urinary bladder and CECT scan of the thoracoabdominal region [Figure 1]c showed a well-defined enhancing lesion in the segment III of the liver and enhancing soft-tissue lesion involving left-sided 5th rib. The patient underwent bronchoscopy guided biopsy for the right hilar lung lesion and transurethral resection of the urinary bladder lesion. The bronchoscopic biopsy specimen and as well as transurethral resected specimen showed metastasis tumor cells of a follicular pattern from the thyroid carcinoma origin and immunohistochemistry showed tumor cells express of PAX8 and TTF-1. These features were suggestive of metastases from carcinoma of the thyroid follicular origin. The patient underwent near-total thyroidectomy with right supraclavicular lymph nodal dissection. The follicular thyroid carcinoma was demonstrated on the thyroid surgical specimen. Postthyroidectomy stimulated serum thyroglobulin level was >300 ng/mL.{Figure 1}

Postthyroidectomy and post excision of urinary bladder lesion, 18F-FDG-PET/CT scan [Figure 2]a was ordered for prognostication and to look for other metastatic sites. Maximum intensity projection image shows FDG avid mediastinal lymph nodal lesions, liver lesions, large-sized soft lesions on the left thoracic region and multiple skeletal lesions. Fused images of 18F-FDG PET/CT [Figure 2]a showed FDG avid enlarged right paratracheal lymph nodes, FDG avid lytic lesion in the right humerus, FDG uptake in segment III liver lesion and FDG avid soft tissue lesion involving left-sided 5th rib and FDG-avid lytic lesion in D6 vertebra. Subsequently, the patient was treated with 131I radioiodine therapy. Posttherapy 131I radioiodine scan [Figure 2]b showed good tracer concentration in thyroid bed and soft-tissue lesion involving left-sided 5th rib and faint tracer uptake in the right humerus and right-sided lung lesions. In contrast, the other skeletal, pulmonary and hilar nodal lesions were 131I negative (the metastatic urinary bladder lesion was not present during the scan, as the patient had undergone complete excision during biopsy of the same prethyroidectomy).{Figure 2}

 Discussion



Multiple sites with metastatic involvement of more than one organ were seen in about 10% of patients with metastatic DTC.[8] The epidemiological data in DTC with rare metastatic sites are not available and unknown. Therefore, documentation of these rare sites is important as they would demonstrate a significant impact on patient management. The American Thyroid Association recommends an FDG-PET scan in high-risk patients with elevated serum Tg (generally >10 ng/mL) and negative radioactive iodine scan.[9] It is usually believed that radio-iodine-avid lesions are not FDG avid and FDG-avid lesions are not iodine avid. Noniodine avid lesions are believed to be due to dedifferentiation. However, in this case, some lesions are both FDG and I-131 avid and some are only FDG avid. Studies in intermediate-to-high risk patients have also reported similar findings.[10],[11] Overall, in this case, FDG-PET detected more lesions than posttreatment I-131 scan.

Inter-lesional heterogeneity may be present in DTC. 18F-FDG PET/CT and 131I scans are helpful in detecting metastatic sites with inter-lesional heterogeneity. The detection of metastatic lesions with inter-lesional heterogeneity in these patients is very useful for both therapeutic and prognostic purposes. The interesting feature of the present case was extremely rare metastasis to the urinary bladder with multi-organs metastatic disease to unusual locations in DTC. These multi-organ lesions were deciphered on the combined study of 18F-FDG-PET/CT scan and 131I posttreatment scintigraphy.

 Conclusion



The documentation of rare site metastatic disease and the combined use of 18F-FDG PET/CT and 131I scans by detection metastatic sites with inter-lesional heterogeneity in this patient of DTC were helpful for both therapeutic and prognostic purpose.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the legal guardian has given his consent for images and other clinical information to be reported in the journal. The guardian understands that names and initials will not be published and due efforts will be made to conceal identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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