FAPI PET/CT Outperforms MRI and FDG PET/CT in Tumor Delineation for Low-grade Nasopharyngeal Papillary Adenocarcinoma

Low-grade nasopharyngeal papillary adenocarcinoma (LGNPPA) is a rare entity. We report a 27-year-old man with a 1-year history of bloody postnasal drip. MRI revealed a protuberance on the roof and posterior wall of the nasopharynx with contrast enhancement. ¹⁸ F-FDG PET/CT showed mild uptake with poorly defined lesion extent, whereas ¹⁸ F-FAPI PET/CT demonstrated intense uptake confined to the tumor with clear boundaries. No metastases were detected. Postoperative pathology confirmed LGNPPA, and the tumor boundary delineated on FAPI PET/CT precisely matched the pathologic extent. This case suggests that FAPI PET/CT may be superior to FDG PET/CT and MRI for tumor delineation in LGNPPA.