Clinicopathological features and lymph node metastatic patterns of gastric mixed adenoneuroendocrine carcinoma.

Aims: Mixed adenoneuroendocrine carcinoma (MANEC), also known as high- grade mixed neuroendocrine-non-neuroendocrine neoplasm (MiNEN) in the World Health Organization (WHO) classification of tumors of the endocrine organs (2017), is a rare gastric malignancy. Here, we present 10 cases of gastric MANEC and analyse their clinicopathological features and lymph node metastatic patterns.

Methods And Results: Six patients were male, and four were female. The mean age of the patients was 67.9 years. Grossly, most tumors presented as ulcerative mass, located in gastric fundus or/and cardia. Microscopically, the neuroendocrine component, large cell neuroendocrine carcinoma in most cases (8/10), constituted 30-70% of the whole tumor. It was diffusely positive for CD56 or/and synaptophysin in all cases, but negative for chromogranin A in 9 cases. Ki-67 index was 50-80% in neuroendocrine component. The glandular component was moderately (6/10) or poorly (4/10) differentiated adenocarcinoma. Nine of 10 cases were positive for lymph node metastasis, with pure neuroendocrine component (6/9), or pure glandular component (1/9), or mixed components (2/9). The patients were treated with surgery, combining with chemotherapy (4/10), radiotherapy (2/10) and immunotherapy (1/10). Five patients died from tumor progress, with an average survival time of 18.6 months. The dead cases had predominant neuroendocrine component in primary tumor or in metastatic lymph nodes.

Conclusions: Neuroendocrine component may determine the clinical behavior and outcome in gastric MANEC. Different metastatic component makes the selection of chemotherapy protocol more challenging.