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INTERESTING IMAGE
Year : 2021  |  Volume : 36  |  Issue : 4  |  Page : 447-448  

Ectopic parathyroid adenoma mimicking as a neuroendocrine tumor on Ga68- DOTANOC positron emission tomography/computed tomography imaging


1 Department of Nuclear Medicine, Post Graduate Institute of Medical Education and Research, Chandigarh, India
2 Department of Endocrinology, Post Graduate Institute of Medical Education and Research, Chandigarh, India

Date of Submission06-May-2021
Date of Decision18-Jun-2021
Date of Acceptance22-Jun-2021
Date of Web Publication15-Dec-2021

Correspondence Address:
Dr. Rajender Kumar
Associate Professor, Department of Nuclear Medicine, Postgraduate Institute of Medical Education and Research, Chandigarh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijnm.ijnm_59_21

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   Abstract 


Parathyroid adenoma sometimes present in ectopic location and may pose a difficulty in both diagnosis and localization. We report a case of a young lady suspected to have neuroendocrine tumor of the mediastinum demonstrating synaptophysin positivity on an initial core needle biopsy. Ga-68 DOTANOC positron emission tomography–computed tomography revealed a somatostatin receptor-expressing lesion in the anterior mediastinum with tracer avid multiple lytic bone lesions. On further biochemical and imaging workup with Tc-99 m SESTAMIBI, a diagnosis of ectopic parathyroid adenoma was made which was further confirmed with surgical excision.

Keywords: Ectopic parathyroid adenoma, Ga-68 DOTANOC positron emission tomography/computed tomography, neuroendocrine tumor, Tc-99 m SESTAMIBI


How to cite this article:
Subramanian K, Krishnaraju VS, Kumar R, Bhadada S, Mittal BR. Ectopic parathyroid adenoma mimicking as a neuroendocrine tumor on Ga68- DOTANOC positron emission tomography/computed tomography imaging. Indian J Nucl Med 2021;36:447-8

How to cite this URL:
Subramanian K, Krishnaraju VS, Kumar R, Bhadada S, Mittal BR. Ectopic parathyroid adenoma mimicking as a neuroendocrine tumor on Ga68- DOTANOC positron emission tomography/computed tomography imaging. Indian J Nucl Med [serial online] 2021 [cited 2022 Oct 4];36:447-8. Available from: https://www.ijnm.in/text.asp?2021/36/4/447/332625



A 43-year-old hypertensive woman presented with history of breathlessness. Initial chest X-ray examination showed mediastinal widening. Noncontrast computed tomography (CT) of the chest showed an anterior mediastinal lesion with extension to the hilar region of the right lung. A core needle biopsy was obtained, and immunohistochemistry (IHC) showed synaptophysin positivity, suggesting a grade I neuroendocrine tumor. Subsequently, a Ga-68 DOTANOC positron emission tomography/CT (PET/CT) was performed for staging the disease, which showed increased tracer uptake in the mediastinal region (Maximum Intensity Projection (MIP) image; [Figure 1]a Trans-axial contrast-enhanced CT [Figure 1]b and fused PET/CT [Figure 1]c images showed a heterogeneously enhancing mass (~5.8 cmx 5.6 cm, with few areas of necrosis) in the anterior mediastinum and extending to the right parahilar region with a SUVmax 9.6. A few tracer avid lytic lesions were also noted in the bilateral iliac bones [[Figure 1]d and [Figure 1]e, SUVmax 6.2] and scapula (SUVmax 4.6).
Figure 1: Maximum intensity projection image (a) of Ga-68 DOTANOC PET/CT demonstrate tracer uptake in the mediastinal region which on transaxial contrast enhanced CT (b) and fused PET/CT (c) images localised to anterior mediastinal mass. Axial CT (d) and fused PET (e) demonstrated tracer avid lytic lesion in the iliac bone.

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The patient was planned for surgical excision of the mass lesion and on preoperative workup, her biochemical investigations demonstrated hypercalcemia (Serum calcium 17.6 mg/dl). Further biochemical evaluation revealed elevated serum parathormone levels (PTH – 1295 pg/ml). A Tc-99 m SESTAMIBI scan was planned to detect the presence of any parathyroid adenoma. Dual time point Tc-99 m SESTAMIBI scan ([Figure 2]a-early image at 10 min postinjection [p. i.] and [Figure 2]b – delayed image 2 h p. i.) revealed the presence of a tracer avid mass lesion (white arrow) in the mediastinum, corresponding to the site of the lesion visualized on Ga-68 DOTANOC PET/CT. She underwent surgical excision of the anterior mediastinal mass. Postoperative histopathology findings confirmed a diagnosis of an ectopic parathyroid adenoma. Her serum PTH levels 1 week after surgery significantly reduced to 82 pg/ml. Ectopic parathyroid adenomas account for about 4%–10% of the pathology in patients with hyperparathyroidism.[1] They can be present anywhere from the base of the tongue to the mediastinum.[2] USG, 4D CT, and Tc-99 m Sestamibi scan are the first line investigations used to evaluate parathyroid adenomas.[3] Tc-99 m SESTAMIBI localizes to parathyroid adenomas because of the presence of high mitochondrial content in oxyphil cells.[4] The parathyroid adenomas are known to express Somatostatin Receptors (SSTRs)[5] and may also show positivity with synaptophysin on IHC, leading to a misinterpretation as a tumor of neuroendocrine origin.[6] Ga68-DOTANOC PET/CT has previously demonstrated detection of parathyroid adenomas at their native location due to the expression of SSTRs.[7] The present case highlights that parathyroid adenomas at the ectopic location may pose a diagnostic challenge because of the resemblance with neuroendocrine tumors with such SSTR targeted imaging agents.
Figure 2: Tc-99m SESTAMIBI scan early image at 10 minutes (a) and delayed image at 2 hrs (b) revealed tracer avidity in the mediastinal mass lesion (white arrow).

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Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
   References Top

1.
Phitayakorn R, McHenry CR. Incidence and location of ectopic abnormal parathyroid glands. Am J Surg 2006;191:418-23.  Back to cited text no. 1
    
2.
Noussios G, Anagnostis P, Natsis K. Ectopic parathyroid glands and their anatomical, clinical and surgical implications. Exp Clin Endocrinol Diabetes 2012;120:604-10.  Back to cited text no. 2
    
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Matthews C, Matthews A, Safavi K. Clinical images: Four-dimensional computed tomography-future of preoperative parathyroid adenoma imaging. Ochsner J 2017;17:220-2.  Back to cited text no. 3
    
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Palestro CJ, Tomas MB, Tronco GG. Radionuclide imaging of the parathyroid glands. Semin Nucl Med 2005;35:266-76.  Back to cited text no. 4
    
5.
Storvall S, Leijon H, Ryhänen E, Louhimo J, Haglund C, Schalin-Jäntti C, et al. Somatostatin receptor expression in parathyroid neoplasms. Endocr Connect 2019;8:1213-23.  Back to cited text no. 5
    
6.
Li J, Chen W, Liu A. Clinicopathologic features of parathyroid carcinoma: A study of 11 cases with review of literature. Zhonghua Bing Li Xue Za Zhi 2014;43:296-300.  Back to cited text no. 6
    
7.
Arora S, Damle NA, Passah A, Yadav MP, Ballal S, Aggarwal V, et al. Incidental detection of parathyroid adenoma on somatostatin receptor PET/CT and incremental role of 18F-fluorocholine PET/CT in MEN1 syndrome. Nucl Med Mol Imaging 2018;52:238-42.  Back to cited text no. 7
    


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