Gastric mixed adenoneuroendocrine carcinoma occurring 30 years after a gastroenterostomy

Abstract

Gastroenteropancreatic neuroendocrine carcinomas (GEP-NENs) represent a heterogeneous group of rare tumors. The incidence of GEP-NENs has increased worldwide over the past decades, with the small intestine, rectum, and pancreas as the most common tumor locations. The epidemiological characteristics, pathogenesis and treatment have raised many questions, and some of them are still being debated. Here, we report a case of gastric collision tumor with large-cell neuroendocrine carcinoma and adenocarcinoma. A 73-year-old male patient with a history of gastric resection performed 30 years ago, with no medical records revealing the type of resection or the reconstructive way, presented with epigastric pain. The endoscopy revealed a solid, ulcerated mass at the gastrojejunal anastomosis site from which a tissue biopsy was taken, which was reported as adenocarcinoma. For staging, the patient underwent an abdominal CT scan, which showed the thickening of the gastric wall adjacent to anastomosis and perilesional adenopathy. The patient underwent a subtotal gastrectomy and regional lymphadenectomy. A diagnosis of large-cell neuroendocrine carcinoma developed on the gastric stump associated with isolated foci of moderately differentiated tubular adenocarcinoma pT3N1G3 was made. Immunohistochemical analysis is essential for the diagnosis and classification of the lesion. To confirm the diagnosis, Chromogranin A and Synaptophysin are needed, and for prognostic evaluation the identification of Ki-67 and mitotic figure count are required.