A Case of Gastric Cancer with Residual Tumor Only in the Para-Aortic Lymph Nodes after Systemic Chemotherapy followed by Conversion Surgery.

We report the case of a 60-year-old male who was diagnosed with gastric cancer. Upper gastrointestinal endoscopy indicated advanced cancer in the posterior wall of the gastric body. Biopsy revealed poorly differentiated adenocarcinoma. Abdominal computed tomography demonstrated thickening of the gastric wall and enlargement of the regional lymph nodes and of the para-aortic lymph nodes (PAN). The involvement of the PAN extended from the celiac axis to the caudal area of the inferior mesenteric artery [cT3N3aH0P0M1(LYM), stage IV]. Systemic chemotherapy was initiated. After 3 courses of S-1 plus cisplatin combination chemotherapy, the primary lesion and the enlarged lymph nodes revealed marked regression except for a minute residual lesion in the lymph nodes. Upon obtaining informed consent, open distal gastrectomy, D2 lymphadenectomy with PAN dissection, and Roux-en-Y reconstruction were performed. The patient was discharged from the hospital 35 days after the operation. Histopathological examination of the resected samples revealed malignant cells only in the PAN, not in the stomach or in the regional lymph nodes [ypT0N0M1(LYM), stage IV]. Currently, the patient is undergoing postoperative adjuvant chemotherapy with S-1 and has remained well without any recurrence after 6 months following surgery.