Ga-68 FAPI-04 PET/CT detection of repeatedly biopsy-negative poorly differentiated gastric adenocarcinoma: a case report.

False-negative endoscopic biopsy may delay the diagnosis of infiltrative gastric cancer, particularly in poorly differentiated or signet-ring cell phenotypes. We report a 56-year-old man with progressive abdominal distension, nausea, vomiting, weight loss, and epigastric pain. Three endoscopic biopsies performed before and after transfer to our hospital showed chronic inflammation without definite malignancy. F-18 FDG PET/CT demonstrated slightly increased and indistinct uptake compared with the liver in the thickened gastric antrum wall, whereas subsequent Ga-68 FAPI-04 PET/CT showed intense uptake with clearer lesion delineation. Because of progressive gastric outlet obstruction and persistent clinical suspicion, distal gastrectomy was performed for symptom relief and definitive diagnosis. Final histopathology confirmed poorly differentiated gastric adenocarcinoma with partial signet-ring cell morphology. The patient subsequently received postoperative XELOX chemotherapy and remained clinically stable at the 7-months follow-up. This case suggests that Ga-68 FAPI-04 PET/CT may serve as a problem-solving adjunct when repeated endoscopic biopsies are non-diagnostic but suspicion for infiltrative gastric cancer persists.