99m Tc-FAPI SPECT/CT Provides Superior Diagnostic Performance to 18 F-FDG in Poorly Differentiated Gastric Adenocarcinoma.

We present the case of a 52-year-old woman with a history of poorly differentiated gastric adenocarcinoma who developed early satiety after gastrectomy and chemotherapy. Her CT and FDG PET/CT did not clearly show recurrence, but the 99m Tc-FAPI SPECT/CT scan detected all peritoneal and omental metastatic deposits with excellent clarity. Because FAPI targets activated stromal tissue, it is especially effective in poorly differentiated and mucinous tumors with limited FDG uptake. In this patient, FAPI revealed small peritoneal lesions missed by other imaging, highlighting its important role in detecting recurrence and guiding management.