Thyroid Research and Practice

CASE REPORT
Year
: 2016  |  Volume : 13  |  Issue : 1  |  Page : 30--32

Sternal metastasis from dedifferentiated thyroid cancer: Value of 18F-fluorodeoxyglucose positron emission tomography–computed tomography imaging in thyroglobulin elevated negative iodine scan syndrome


Meghana Prabhu1, Nalini Raju2, Subramanian Kannan3, RL Vijayaraghavan1,  
1 Department of Nuclear Medicine, Narayana Hrudayalaya Institute of Medical Sciences, Bengaluru, Karnataka, India
2 Department of Pathology, Narayana Hrudayalaya Institute of Medical Sciences, Bengaluru, Karnataka, India
3 Department of Endocrinology, Narayana Hrudayalaya Institute of Medical Sciences, Bengaluru, Karnataka, India

Correspondence Address:
R L Vijayaraghavan
Basement, Multispeciality and Cancer Hospital Building, Narayana Health City, Plot No. 258A, Bommasandra Industrial Area, Anekal Taluk, Hosur Road, Bengaluru - 560 099, Karnataka
India

Abstract

Differentiated thyroid cancers are generally iodine avid and have an indolent growth rate. Dedifferentiation of thyroid cancer is rare and is commonly accompanied with more aggressive growth, metastatic spread, and loss of iodine avidity. 18F-fluorodeoxyglucose positron emission tomography–computed tomography (18F FDG PET–CT) plays an important role in identifying the extent of dedifferentiated disease and aids further management. The present case highlights the importance of 18F FDG PET-CT imaging in thyroglobulin elevated negative iodine scan syndrome clinically presenting with sternal metastasis.



How to cite this article:
Prabhu M, Raju N, Kannan S, Vijayaraghavan R L. Sternal metastasis from dedifferentiated thyroid cancer: Value of 18F-fluorodeoxyglucose positron emission tomography–computed tomography imaging in thyroglobulin elevated negative iodine scan syndrome.Thyroid Res Pract 2016;13:30-32


How to cite this URL:
Prabhu M, Raju N, Kannan S, Vijayaraghavan R L. Sternal metastasis from dedifferentiated thyroid cancer: Value of 18F-fluorodeoxyglucose positron emission tomography–computed tomography imaging in thyroglobulin elevated negative iodine scan syndrome. Thyroid Res Pract [serial online] 2016 [cited 2020 Mar 30 ];13:30-32
Available from: http://www.thetrp.net/text.asp?2016/13/1/30/168902


Full Text

 Introduction



Differentiated thyroid cancer is typically an indolent disease with excellent long-term prognosis. Dedifferentiated thyroid carcinoma is a rare and distinct diagnostic entity and its incidence is 2–3% of thyroid cancers [1] and are commonly accompanied with more aggressive growth, metastatic spread, and loss of iodine avidity. This may be related to decreased expression of thyroid-specific genes namely sodium iodide symporter, thyroglobulin (Tg) genes, and transcriptional factors.[2] Patients with dedifferentiated thyroid cancer generally present with elevated Tg but a negative iodine (131 I) whole body scan due to loss of iodine avidity, a presentation coined as Tg elevated negative iodine scan syndrome (TENIS). Do et al.,[3] reported an incidence of bone metastases of only 0.4% in patients with papillary thyroid carcinoma (PTC). 18F-fluorodeoxyglucose positron emission tomography–computed tomography (18 F FDG PET–CT) plays an important role in identifying the extent of dedifferentiated disease and aids further management.

 Case Report



A 69-year-old male with a history of smoking and hypertension initially presented with progressive left side neck swelling. Neck Ultrasonography showed a large left sided thyroid nodule replacing the left lobe of thyroid measuring 7.7 cm × 5.3 cm × 4.5 cm and a subcentimeter nodule on the right lobe. The nodule on the left lobe was vascular and showed microcalcifications. Bilateral Level III, IV and VI cervical lymph nodes were seen with the largest lymph node in left Level VI compartment measuring 4.8 cm × 3.8 cm. All the lymph nodes had distorted architecture and peripheral vascularity. Fine-needle aspiration cytology (FNAC) of the nodule and the left Level VI cervical lymph node was confirmatory for papillary thyroid carcinoma. The patient underwent total thyroidectomy, bilateral neck lymph node dissection and also sternotomy to remove Level VII cervical lymph nodes. Histopathology report showed multifocal papillary carcinoma (classical variant) with positive surgical margins, Stage IVA (tumour, node, metastases) - p T4 N1b M ×. Since, he was considered American Thyroid Association high-risk category and had an R1 resection, 5580 cGy of radiotherapy was given to the anterior neck in 31 fractions over a period of 3 months to address the residual disease. Three months later, after withdrawal of thyroid hormone for 3 weeks, he presented with elevated Tg > 1000 ng/mL [1.4–7.8] and Tg antibody of 53.5 IU/mL [0–115] and thyroid stimulating hormone > 150 µIU/L). Whole body radioactive iodine scan did not reveal any radioiodine avid metastasis except for a questionable focus of uptake in the mid anterior chest [Figure 1]. He was advised 18 F FDG PET-CT scan to screen for the dedifferentiated disease, but the patient was lost to follow-up. Four months later, the patient presented again with a rapidly progressive hard chest wall swelling.18 F FDG PET-CT [Figure 2]a,[Figure 2]b,[Figure 2]c showed a large hypermetabolic lytic lesion with soft tissue component in the sternal manubrium measuring 5.8 cm × 4.1 cm × 5.8 cm with maximum standardized uptake value of 18.3. This metastatic bone lesion was seen to extend into the superior mediastinum abutting junction of the ascending and arch of the aorta with indistinct fat planes [Figure 2]c. Hypermetabolic lytic lesion with intraspinal extension was seen in the posterior body of T4 and T5 vertebrae causing mild spinal canal stenosis [Figure 2]c. Numerous FDG avid and non-FDG avid pleural based and parenchymal soft tissue nodules seen in bilateral lungs were suggestive of bilateral pulmonary metastases. FNAC from the sternal mass showed numerous atypical cells with papillary configuration and eccentric nuclei. Occasional nuclear grooves and intranuclear cytoplasmic inclusions were seen, and features were consistent with metastatic PTC [Figure 3]. The patient then received external beam radiotherapy (dose of 3000 cGy in 12 fractions to vertebral region [T5–T7]) and 4050 cGy in 16 fractions to the sternal region. During 6 months follow-up a noncontrast CT scan of chest showed interval increase in size of the lytic lesion in the sternal manubrium (7.1 cm × 4.0 cm × 8.0 cm) with an interval appearance of cystic component extending up to the skin [Figure 4]a,[Figure 4]b,[Figure 4]c. The features were consistent with disease progression and the patient was referred to medical oncology for chemotherapy.{Figure 1}{Figure 2}{Figure 3}{Figure 4}

 Discussion



Sternal metastasis from intrathoracic or extrathoracic malignancy is rare. Most sternal metastases arise from breast cancer, and only a few cases of sternal metastasis arising from PTC have been reported.[4] An increased frequency of lung and bone disease has been reported in follicular thyroid carcinoma because dissemination is predominantly hematogenous, which is less frequent in the PTC. Do et al.,[3] reported an incidence of bone metastases of 0.4% in patients with PTC. Patients with the sternal disease may present with superior vena cava syndrome, with consequent circulatory arrest and immediate death. Patients with metastases to bones have poor survival when compared to patients with metastasis to cervical lymph nodes and lung.[5] Current guidelines advise bone metastases to be treated with a combination of surgery, external beam radiotherapy and 131 Iodine therapy for iodine avid metastasis.[6] Surgical excision is recommended for accessible solitary, isolated metastases. Various techniques for closure and coverage of the defect after resection of the sternal lesion have been described. Autoplastic reconstruction is indicated for smaller defects, while larger defects usually require alloplastic materials, especially in the case of chest instability after resection.[5] Given the anatomical location and proximity to the arch of the aorta, as well as patients preference, the metastatic lesion was not operated in present study.

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