Unilateral Chronic Parotitis With 68 Ga-DOTA-FAPI-04 PET/CT and 18 F-FDG PET/CT Imaging in a Case of a Patient With Papillary Thyroid Carcinoma.

The 68 Ga-FAPI (fibroblast activation protein inhibitor) radiotracer is a novel and versatile tool in nuclear medicine, exhibiting potential for use in various conditions due to its significant upregulation in cancerous and inflammatory conditions, particularly those involving fibrotic and infectious processes. In this report, we present the case of a patient with papillary thyroid carcinoma who underwent total thyroidectomy and iodine therapy. He was referred because of high thyroglobulin despite negative diagnostic radioiodine imaging (TENIS syndrome). The patient underwent 18 F-FDG and 68 Ga-DOTA-FAPI-46 PET/CT imaging for metastatic workup and treatment planning. FAPI uptake was observed in the right parotid gland (with no FDG uptake), prompting a 99m TcO 4- salivary scintigraphy. Subsequently, a diagnosis of chronic sialadenitis was made.