Diagnostic challenge in parathyroid imaging: incidental schwannoma mimicking primary hyperparathyroidism on ¹⁸F-fluorocholine PET/CT

Introduction

Schwannomas, or neurilemomas, are non-malignant tumors arising from Schwann cells, which are responsible for producing the myelin sheath around nerves. Typically these tumors are well-encapsulated, slow-growing and most commonly located in the head and neck regions [1]. Occurrence in the mediastinum or abdominal cavity is relatively rare. Even though they are mostly benign, their clinical presentation may vary depending on their size and anatomical location, potentially leading to compressive symptoms. Diagnosis is typically established through a combination of clinical evaluation and imaging modalities, including magnetic resonance imaging (MRI) and computed tomography (CT), complemented by electrophysiological studies and histopathological confirmation via biopsy.

¹⁸F-fluorocholine (¹⁸F-FCH) positron emission tomography/computed tomography (PET/CT) is a molecular imaging method primarily used in oncology, most notably prostate cancer, as well as in the diagnosis of parathyroid gland disorders, in the first place primary hyperparathyroidism. Choline serves as a precursor in the biosynthesis of phosphatidylcholine, a fundamental component of cell membranes. Consequently, cells with increased membrane turnover exhibit enhanced choline uptake [1]. This mechanism of ¹⁸F-FCH accumulation can lead to the detection of various incidental findings such as schwannomas which can be a demanding diagnostic challenge. Our group reports the first documented case of a mediastinal schwannoma incidentally identified due to increased ¹⁸F-FCH uptake on PET/CT performed in the context of suspected primary hyperparathyroidism. Notably, the lesion showed no uptake on prior dual-phase ^99mTc-sestamibi (MIBI) single-photon emission computed tomography/computed tomography (SPECT/CT) imaging and was not visualized on cervical ultrasonography due to its anatomical location. This case underscores the importance of including schwannomas and schwannoma-like lesions in the differential diagnosis of fluorocholine-avid findings, as they may represent potential sources of false-positive results in ¹⁸F-FCH PET/CT imaging.

Publication History

Received: 28 June 2025

Accepted: 14 July 2025

Article published online:
22 August 2025

• References

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