Composite glandular and endocrine tumors of the stomach with pancreatic acinar differentiation.

Composite tumors of the stomach consisting of mixed glandular and endocrine components are rare. We report 3 cases of composite glandular and endocrine tumors with pancreatic acinar differentiation in the stomach with their clinicopathologic findings. The patients' presenting symptoms were variable and included abdominal pain, gastrointestinal hemorrhage, and weight loss. One patient with abdominal pain also had an elevated serum lipase level, clinically mimicking acute pancreatitis. The histology of these tumors was similar. They showed admixture of well-differentiated endocrine components with acinar and glandular components. The glandular component consisted of columnar epithelial cells resembling gastric foveolar or intestinal goblet cells, consistent with a well-differentiated adenocarcinoma. A panel of histochemical and immunohistochemical stains was performed, which included PAS, Alcian blue, Mib1, CEA, cytokeratin 7, cytokeratin 20, Muc2, Muc5AC, chromogranin, synaptophysin, trypsin, chymotrypsin, lipase, insulin, gastrin, serotonin, and pancreatic polypeptide. While the immunoreactivity for cytokeratin 7, cytokeratin 20, Muc2, Muc5AC, and CEA was largely restricted to the glandular component, the endocrine and pancreatic acinar markers showed marked variability and overlap. All cases showed immunoreactivity for at least one of the exocrine pancreatic enzymes, and all expressed endocrine differentiation. Some degree of amphicrine differentiation was suggested in all cases. Two cases showed metastases in perigastric lymph nodes, which histologically resembled the primary tumor. In summary, these tumors represent another distinct type of composite glandular and endocrine gastric neoplasm with pancreatic acinar differentiation.