Composite Neuroendocrine Carcinoma with Adenocarcinoma of the Stomach Mimicking Double Primary Cancer

ABSTRACT

A 67-year-old man presented with a 3-month history for intermittent epigastric pain and postprandial discomfort. Upper gastrointestinal endoscopy and contrast-enhanced axial computed tomographic scan demonstrated two separate tumors of the gastric antrum and the duodenal second portion, suggestive of the preoperative diagnosis of a double primary cancer. Pancreaticoduodenectomy with lymph node dissection was performed, and the microscopic features and immunohistochemical profiles of the resected specimen confirmed the diagnosis of the composite neuroendocrine carcinoma with adenocarcinoma of the stomach (mixed exocrine-endocrine carcinoma).