Objective  To explore the clinicopathologic characteristics of gastric mixed adenoneuroendocrine carcinoma (MANEC).

  Methods  From January 2011 to December 2016, the clinical and pathological data of 35 patients with gastric MANEC who were diagnosed and surgically treated in Tianjin Medical University Cancer Institute and Hospital were analyzed retrospectively.

  Results  The average age of the 32 men and 3 women in this study was 61.6±7.5 years. Tumor locations were as follows: 17 related to gastric cardia, 9 related to gastric body, 8 related to gastric antrum, and 1 related to gastric stump. Clinical symptoms were non-specific and the diagnosis relies on postoperative pathological examination. Using the histological microscope, the affected structures were detected in neuroendocrine systems and tissue linings. Immunohistochemical staining showed that carcinoembryonic antigen (CEA) and cytokeratins 8 and 18 (CK8/18) were expressed in 32 and 33 adenocarcinoma-related cases, respectively, whereas synaptophysin (Syn) and chromogranin A (CgA) were revealed in 33 and 27 neuroendocrine-related cases, respectively. All patients received surgical resection. A total of 17 incidents of death were reported at three years after the operation, and most of the patients were at clinical stage Ⅲ or Ⅳ.

  Conclusion  Gastric MANEC is a rare neoplasm and is often diagnosed at its advanced stage and mainly occurs in the aged population. Neuroendocrine structures and glandular tissues are the most frequent location of such condition. Diagnosis relies on both immunohistochemical and histological examinations. Surgical resection is the most effective treatment, but the prognosis of this condition remains poor.