Molecular Imaging in Parathyroid Carcinoma Management: A Comprehensive Review

Parathyroid carcinoma (PC) is an exceedingly rare endocrine malignancy, accounting for less than 1% of all primary hyperparathyroidism (pHPT) cases. It typically presents with pronounced hypercalcemia and markedly elevated parathyroid hormone (PTH) levels. Accurate imaging plays a pivotal role in diagnosis, staging, surgical planning, and long-term surveillance, although differentiating PC from benign disease on imaging remains a significant challenge. A multimodal imaging strategy combining cervical ultrasonography (US) and nuclear medicine techniques provides high sensitivity for lesion detection. Ultrasonography with advanced detective flow imaging allows detailed anatomical assessment and evaluation of vascular patterns of the primary tumor. [$^{99m}$Tc]Tc-methoxyisobutylisonitrile ([$^{99m}$Tc]Tc-MIBI) scintigraphy frequently demonstrates prolonged tracer retention in PC, while [$^{18}$F]fluorocholine positron emission tomography/computed tomography (PET/CT) and positron emission tomography/magnetic resonance (PET/MR) imaging have shown superior performance for detecting both primary tumors and metastatic disease due to its higher spatial resolution and higher molecular sensitivity. [$^{18}$F]FDG PET serves as an adjunct modality for identifying aggressive, metabolically active lesions. Emerging radiotracers such as [$^{18}$F]-fibroblast activation protein inhibitor ([$^{18}$F]FAPI) and [$^{68}$Ga]Ga-trivehexin have shown potential in cases where initial imaging is inconclusive. Theranostic strategies that integrate molecular imaging with targeted radioligand therapy may transform PC management by enabling personalized treatment approaches tailored to each tumor's biological and imaging characteristics. This review aims to evaluate available imaging modalities for PC diagnosis and provide guidance for their clinical application.