Alteration of tumor characteristics following neoadjuvant treatment in gastric adenocarcinoma: a case report

A 69-year-old female was admitted to the hospital with abdominal pain and distension. Gastroscopy revealed an irregular protruding lesion on the lesser curvature of the gastric fundus, and pathological examination indicated moderately to poorly differentiated adenocarcinoma. Enhanced abdominal computed tomography (CT) identified a space-occupying lesion at the gastric fundus with multiple enlarged lymph nodes. The initial diagnosis was moderately to poorly differentiated adenocarcinoma, cT3N3M0 (Stage IIIa). The patient subsequently underwent neoadjuvant therapy comprising albumin-bound paclitaxel, camrelizumab, oxaliplatin, and S-1.After four cycles, the tumor significantly reduced in size, with restaging at yT2N2M0 (Stage IIb). Following multidisciplinary team (MDT) consultation, the patient underwent radical total gastrectomy with esophagojejunostomy. Postoperative recovery was uneventful, and the patient was discharged in improved condition. Notably, postoperative pathological analysis revealed a neuroendocrine tumor, demonstrating an alteration in tumor histology after neoadjuvant therapy for gastric cancer (GC).