Synchronous Large Gastrointestinal Stromal Tumor and Adenocarcinoma in the Stomach Treated with Imatinib Mesylate Followed by Total Gastrectomy

Herein we report on a case of synchronous large gastrointestinal stromal tumor (GIST) and adenocarcinoma of the stomach treated with radical surgery following neoadjuvant therapy with imatinib mesylate. A 58-year-old man was referred to our hospital with a large mass in the peritoneal cavity. Abdominal computed tomography showed a large mass measuring 21×20×14 cm in the left upper peritoneal cavity. Esophagogastroduodenoscopy revealed a large elevated lesion in the upper body and a depressed lesion in the lower gastric body near the lesser curvature. Biopsy specimens revealed GIST in the large elevated lesion and signet-ring cell carcinoma in the depressed lesion. Because of the large size of the GIST, the patient was treated with neoadjuvant therapy with imatinib mesylate (400 mg/day) for 5 months. After confirmation of a marked decrease in tumor size following imatinib mesylate therapy, the patient underwent total gastrectomy and regional lymph-node dissection with distal pancreatectomy and splenectomy. Pathological examination confirmed the diagnosis of high-risk GIST and signet-ring cell carcinoma invading the muscularis propria with one lymph-node metastasis. At the time of writing, the patient was receiving postoperative chemotherapy using oral fluoropyrimidine (S-1) without evidence of disease recurrence for 4 months after surgery. In addition to the present case, we provide a retrospective review of another 15 patients who were diagnosed with synchronous GIST in the stomach and primary gastric adenocarcinoma.