Nivolumab exerts therapeutic effects against metastatic lesions from early gastric adenocarcinoma with a small proportion of neuroendocrine carcinoma after gastrectomy: a case report.

Gastric neuroendocrine carcinoma (NEC) is an aggressive disease with high metastatic ability. Gastric cancer has intra-tumoral and intra-patient heterogeneity and may contain NEC. We discuss the case of a 75-year-old man who underwent distal gastrectomy for early gastric cancer.