Gastric collision tumor of large cell neuroendocrine carcinoma and adenocarcinoma--a case report.

Large cell neuroendocrine carcinomas (LCNECs) of the stomach are rare and represent only a small percentage of all gastric endocrine tumors. Here we report a case of a rare combination of gastric LCNEC concurrent with gastric adenocarcinoma. A 50-year-old man presented with heartburn sensation for 2 weeks. An endoscopic evaluation revealed a relatively well-demarcated ulcerative elevated lesion at the lower body of the stomach. Grossly, the gastric mass was a 5x4.5 cm-sized ulcerative fungating lesion. Microscopically, two separated lesions were recognized. The main lesion showed neuroendocrine morphology, such as nests and trabeculae. Most of the tumor cells had large, vesicular nuclei with prominent eosinophilic nucleoli, variable amounts of eosinophilic cytoplasm, and immunoreactivity for synaptophysin and chromogranin A. The other lesion was a well-differentiated adenocarcinoma of early gastric cancer type IIa located adjacent mucosa of the main lesion. We diagnosed this lesion as gastric LCNEC concurrent with focal adenocarcinoma, collision type.