[A Case of Conversion Surgery following Chemotherapy for HER2-Positive Advanced Gastric Cancer].

A 73-year-old female was referred to the gastroenterological department of our hospital for examination because of anemia. CA19-9 increased to 1,392 U/mL, and upper endoscopy revealed type 2 gastric cancer extending from the anterior wall to the lesser curvature in the lower part of the gastric body. Biopsy specimens revealed well-differentiated tubular adenocarcinoma, and HER2 was positive immunohistologically. Contrast-enhanced CT revealed wall thickness of the lower part of the gastric body with marked lymph node swelling beside the lesser curvature and a low-density nodule measuring 10 mm in diameter with rim enhancement in segment 5 of the liver, indicative of liver metastasis. Thus, she was diagnosed with unresectable advanced gastric cancer(cT3cN2M1, HEP, cStage ⅣB), and combined chemotherapy with capecitabine, cisplatin, and trastuzumab was administered. After 7 courses, CA19-9 normalized, and upper endoscopy revealed a scar of the primary tumor, and cancer was not detected in the biopsy specimen. On contrast-enhanced CT, lymph nodes beside the lesser curvature shrank significantly, and liver nodules disappeared. She was referred to our department for conversion surgery, and distal gastrectomy with D2 lymph node dissection was performed 7 months after her first visit to our hospital. Pathologically, tumor invasion was restricted to the lamina propria, and lymph node metastasis was not observed(ypT1aN0M0, ypStage Ⅰ A). She was discharged on postoperative day 13 and is alive without tumor recurrence at 7 months after surgery. She is not currently undergoing adjuvant chemotherapy.