Squamous Cell Carcinoma of the Tonsil Unmasked by 68 Ga-FAPI-46 PET/CT.

We reported 18 F-FDG and 68 Ga-FAPI-46 PET/CT findings in a 55-year-old woman with metastatic squamous cell carcinoma of the left neck. 18 F-FDG PET/CT was negative for the detection of primary malignancy. On 68 Ga-FAPI PET/CT, increased radiotracer uptake was noted in the left palatine tonsil, whereas low background uptake was observed in the right palatine tonsil. Based on the PET/CT findings, the patient underwent clinical examination and biopsy of the left tonsil. Histology demonstrated the presence of a squamous cell carcinoma of the tonsil. The case demonstrated the added value of 68 Ga-FAPI-46 PET/CT for locating the primary malignancy in cancer of unknown primary.