A 77-year-old man underwent endoscopic submucosal dissection (ESD) of a type 0-IIc tumor located in the cardiac part of the stomach. The pathological diagnosis of the tumor was poorly differentiated tubular adenocarcinoma with submucosal invasion depth;therefore, radical gastrectomy was also performed. After 1 year and 10 months, liver metastasis was detected because of which partial liver resection was performed. The pathological diagnosis of the tumor was neuroendocrine carcinoma (NEC). The pathology of the ESD specimen was re-examined, and a diagnosis of gastric NEC was made;furthermore, the liver tumor was regarded as metachronous metastasis. Despite the radical excision of the stage IA tumor, metastasis occurred. Chemotherapy with S-1 alone was successfully performed after the liver resection while considering the advanced age of the patient. Follow-up revealed no signs of recurrence at 1 year and 4 months after the treatment, indicating that the S-1 therapy may be considered for treating NEC in elderly and medically compromised patients owing to its mild side effects.