Gastrointestinal Stromal Tumor with Concomitant Diffuse Large B-cell Lymphoma of the Stomach—A Case Report—

Abstract

A 77-year-old man underwent esophagogastroduodenoscopy, which revealed a flat ulcer with a raised margin along the lesser curvature of the lower gastric body. Based on biopsy findings, he was diagnosed with diffuse large B-cell lymphoma. During the procedure, we observed a mass adjacent to the gastric wall along the lesser curvature of the upper gastric body, which was suspicious for an enlarged lymph node. The tumor in the lower gastric body disappeared following a course of 5 cycles of rituximab, cyclophosphamide, hydroxydaunorubicin, vincristine sulfate, and prednisone chemotherapy. However, the tumor in the upper gastric body remained unchanged, and ¹⁸F-fluorodeoxyglucose (FDG)-positron emission tomography-computed tomography revealed low FDG uptake, leading to a suspicion of a gastrointestinal stromal tumor (GIST). Endoscopic ultrasound-guided fine-needle aspiration is associated with the risk of dissemination ; therefore, we performed open partial gastrectomy. The tumor was identified in the lesser omentum and originated from the gastric wall. We performed en bloc resection, and the patient was discharged 8 days later. Histopathological examination revealed the tumor measured 33 mm in size, and immunohistochemical examination revealed immunopositivity for CD34+ and c-kit+. Based on these findings, he was diagnosed with low-risk GIST of the stomach. Until the time of writing this report, the patient has shown no relapse for 17 months without adjuvant therapy.