A unique coincidence - Concurrent oncocytic thyroid Carcinoma and tenosynovial giant cell tumor - A case report

Sep 22, 2026

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Oncocytic thyroid carcinoma (OTC) and tenosynovial giant cell tumor (TGCT) are rare neoplasms with distinct behavior, and simultaneous occurrence is rarely documented. A 45-year-old man developed a rapidly enlarging left ankle and foot soft-tissue mass. 18F-FDG PET/CT showed intense thyroid-bed and hypermetabolic musculoskeletal lesions, initially suspected as metastatic disease. Histopathology of the ankle lesion confirmed diffuse-type TGCT (TGCT-D). The case highlights an imaging pitfall: FDG-avid musculoskeletal lesions in known malignancy can represent non-metastatic TGCT, requiring multimodality correlation and biopsy confirmation for appropriate management.

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CategoryHealthcare

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Introduction

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A unique coincidence: Concurrent oncocytic thyroid Carcinoma and tenosynovial giant cell tumor: A case report Fatimah AbuAlJaaz 1, Mahd Foqhaa1, Mohammed abduljabbar Abed2, Ahmed Saad Abdlkadir1, Akram Al-Ibraheem1* 1Nuclear Medicine Department, King Hussein Cancer Center (KHCC), Amman, Jordan 2Radiology Department, King Hussein Cancer Center (KHCC), Amman, Jordan A R T I C L E I N F O | Article type:
Case Report | | --- | | Article history:
Received: 6 Apr 2025
Revised: 20 Feb 2026
Accepted: 21 Feb 2026 | Keywords: Oncocytic thyroid carcinoma Tenosynovial giant cell tumor Whole body iodine scan FDG PET/CT Please cite this paper as: A B S T R A C T tumor their rare- mass emission demonstrated recurrent in. the in with Careful particularly misdiagnosis Oncocytic thyroid carcinoma (OTC) and tenosynovial giant cell (TGCT) are rare neoplasms with distinct biological behavior, and coexistence has not been previously well documented. We report a case of concurrent recurrent OTC and diffuse-type TGCT (TGCT-D) in a 45 year-old man who presented with a rapidly enlarging soft-tissue involving the left ankle and foot. 18F-fluorodeoxyglucose positron tomography/computed tomography (FDG PET/CT) intensely FDG-avid lesions in the thyroid bed consistent with disease, as well as a hypermetabolic infiltrative musculoskeletal lesion the left ankle and foot, initially suspected to represent metastatic spread However, histopathological examination of the ankle lesion established diagnosis ofTGCT-D. This case illustrates an important diagnostic pitfall oncology imaging: FDG-avid musculoskeletal lesions in patients known malignancy do not necessarily represent metastases. integration of clinical information, cross-sectional imaging, MRI, and histopathological confirmation is essential to avoid and to ensure appropriate management. AbuAlJaaz F, Foqhaa M, r Abed MA, Abdlkadir AS, Al-IbraheemA. A unique coincidence: Concurrent oncocytic thyroid carcinoma and tenosynovial giant cell tumor: A case report. Asia Ocean J Nucl Med Biol. 2026; 14(2): 187-192. doi: 10.22038/aojnmb.2026.87172.1625 Introduction To our knowledge, this is the first documented case of the co-occurrence of OTC and TGCT-D. OTC, also referred to as oxyphilic carcinoma and previously known as Hürthle cell tumor, is a rare variant of differentiated thyroid cancer. It account for approximately 3% to 5% of all thyroid cancers, making it considerably less common than other subtypes (1, 2). Histologically, it does not exhibit the distinctive nuclear characteristics of papillary thyroid cancers (PTC) or the features associated with highgrade malignancies (1) . Thyroid cancer is twice as common in women as in men; however, men tend to have a worse prognosis. OTC is rare and is associated with high likelihood of recurrence, metastasis, and a poor prognosis (1, 3). Compared with other types of thyroid cancer, OTC has a higher propensity for metastasis to regional lymph nodes and distant organs, including lungs, liver, and bones (2) . Recent studies have highlighted the role of radioactive iodine (RAI) therapy in management and improving overall survival particularly patients without extensive metastatic disease. Additionally, FDG-PET scan plays a decisive role in diagnosis, assessing disease extent, and treatment response. However, clinicians should remain aware of the potential for false-positive results, therefore clinical correlation always essential (4) . TGCT is a rare, locally aggressive mesenchymal tumor including a group of typically benign, proliferative, and inflammatory conditions that arise from the synovium of joints, bursae, and tendon sheaths. Based on growth patterns and clinical behavior, TGCTs are classified into two subtypes: localized and diffuse (5-7) . It is caused by a mutation in the stromal cells of the synovial membrane, resulting in overproduction of colony-stimulating factor 1 (CSF1) . This overproduct

FAQs

Why is the concurrent occurrence of OTC and TGCT-D considered unusual?

OTC and TGCT are rare tumors, and their coexistence has not been well documented previously, making this report notable.

What imaging findings initially suggested metastatic disease?

FDG PET/CT showed intense FDG-avid lesions in the thyroid bed and a hypermetabolic infiltrative musculoskeletal lesion in the left ankle and foot, which was initially suspected to represent metastasis.

How was the ankle lesion ultimately diagnosed?

Histopathological examination of the ankle lesion established the diagnosis of diffuse-type tenosynovial giant cell tumor (TGCT-D).

Sep 22, 2026

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