[A Case of HER2-Positive Siewert Type I Adenocarcinoma of the Esophagogastric Junction Treated via Neoadjuvant Chemotherapy Followed by Radical Resection].

A 63-year-old man with dysphagia was referred to our hospital. He was found to have a type 2 tumor extending from the lower thoracic esophagus to the esophagogastric junction via upper gastrointestinal endoscopy. A biopsy revealed adenocarcinoma with overexpression of the human epidermal growth factor type 2(HER2). The tumor was type I according to Siewert's classification, as the epicenter of the tumor was 27mm to the oral side from the esophago-gastric junction. The clinical diagnosis was T3N1M1, stage IV according to the Japanese Classification of Gastric Carcinoma, and T3N2M0, stage III per the Japanese Classification of Esophageal Cancer. He was treated with neoadjuvant chemotherapy consisting of 6 courses of capecitabine(1,000mg/m / / 2: days 1-14)plus cisplatin(80mg/m2: day 1)and trastuzumab(8mg/kg: day 1 of the first course, 6mg/kg: day 1 after the second course). Computed tomography(CT)and upper gastrointestinal endoscopy showed shrinkage of the primary esophagogastric cancer and lymph node metastases. The patient had a partial response and underwent radical esophagectomy. The pathological findings revealed a T3N2M0, stage III tumor; the tumor was determined to be Grade 1b owing to the chemotherapeutic effect. At a follow-up examination 1 year and 7 months after the start of chemotherapy, the patient is alive without recurrence.