Mixed Acinar-Neuroendocrine Carcinoma of the Stomach: A Case Report and Review of the Literature

Abstract

Abstract Introduction/Objective Mixed Acinar Neuroendocrine Carcinoma (MACNEC) is rare and usually occurrs in the head of the pancreas. This is an epithelial neoplasm of the pancreas exhibiting both acinar and neuroendocrine differentiation. Each component must represent at least 30% of the tumor. Extrapancreatic acinar cell carcinoma arising in the stomach are also rare and represent <1% of all gastric neoplasms. Here we report a case of MACNEC arising in the stomach of a 60 yo female and we review the literature. Methods The specimen was formalin-fixed and paraffin embedded. 4-microns sections of the tumor block were stained for hematoxylin and eosin and immunostained for CAM5.2, Chromogranin, synaptophysin, trypsin, chymotrypsin, BCL10, HepPar1 and AFP using a Ventana Discovery XT automated system (Ventana Medical Systems, Tucson, Ariz) as per manufacturer’s protocol with proprietary reagents. Results The patient presented with heartburn and weight loss. An upper endoscopy revealed an ulcer along the stomach greater curvature. Endoscopic ultrasound revelaed an hypoechoic round mass involving the submucosa. Imaging showed no lesions in the pancreas. A stomach wedge resection was performed: a 1.2 x 0.6 x 0.5 cm. submucosal tan-brown mass was found. Microscopically the tumor had alternated solid/acinar areas with cords/ribbons neuroendocrine-like areas. Both components were immunohistochemically positive for keratin (CAM 5.2), chromogranin (diffuse), and synaptophysin (patchy). The trypsin, chymotrypsin and BCL10 immunostains were patchy and stained 30 to 40% of the tumor. The immunostains for HepPar-1 and AFP were negative. These results support the diagnosis of MACNEC. Pancreatic heterotopia was not identified in the tissue examined. The margins of resection were free of tumor. The tumor was staged as T1NXMX. The patient has been under close surveillance for 3 years and she has no radiographic evidence of tumor recurrence or metastases. Conclusion We found only 6 prior cases of MACNEC originating in the stomach. They had similar histopathologic and immunohistochemical features. In the absence of a pancreatic lesions, in this patient the tumor may have originated from ectopic pancreatic tissue or from a pluripotent stem cell in the stomach.