Multimodal approach enables R0 resection in advanced gastric adenocarcinoma with enteroblastic differentiation complicated by portal vein tumor thrombus.

Gastric adenocarcinoma with enteroblastic differentiation (GAED) is an extremely rare gastric cancer subtype with high rates of vascular and lymphatic invasion, lymph node and liver metastasis, leading to poor prognosis and early recurrence. We report a 73-year-old woman with stage IV GAED and portal vein tumor thrombus (PVTT) treated with multimodal therapy. She received S-1 plus oxaliplatin (SOX), SOX plus nivolumab, S-1 plus nivolumab, and radiotherapy for PVTT without major adverse events. Imaging showed marked tumor and lymph node shrinkage and complete PVTT disappearance. Laparoscopic distal gastrectomy with D2 dissection achieved R0 resection; pathology confirmed GAED, ypT2N1M0, Stage IIA, with Grade 1b response. This case suggests SOX plus nivolumab is effective for advanced GAED and that radiotherapy for PVTT enables curative surgery. Preoperative chemoradiotherapy and conversion surgery may provide a promising strategy for otherwise unresectable GAED.