FAPI Uptake in Malignant Ascites

We present a 69-year-old man with a history of renal cell carcinoma who previously underwent nephrectomy. He was referred to our department for 99m Tc-FAPI and 99m Tc-PSMA scans (under an investigational protocol) due to a newly diagnosed rising prostate-specific antigen (PSA) level and a suspected retroperitoneal mass of unknown origin. Notably, the patient had a known history of malignant ascites, and his 99m Tc-FAPI scan demonstrated increased radiotracer uptake within the abdominal cavity.