FAPI-negative Papillary Renal Cell Carcinoma With Markedly FAPI-avid Sacral Insufficiency Fracture

We report a 77-year-old woman with papillary renal cell carcinoma showing no increased [68Ga]Ga-FAPI uptake in the primary tumor, while intense sacral FAPI uptake mimicked bone metastasis. MRI findings and 2-year follow-up supported a sacral insufficiency fracture without metastatic disease. This case highlights fracture-related FAPI uptake as an important oncologic imaging pitfall.