胃腺癌化学療法中に原発巣増大をきたし混合型腺神経内分泌腫瘍と診断した 1 例

Gastric mixed neuroendocrine-non-neuroendocrine neoplasm (MiNEN) is an extremely rare form of gastric neoplasm, and its prognosis is often poor. This is a case report wherein the primary site increased during chemotherapy against gastric adenocarcinoma and was diagnosed with gastric MiNEN after total gastrectomy. A 71-year-old man was diagnosed with gastric adenocarcinoma complicated with liver and para-aortic lymph node metastasis. Chemotherapy with S-1, oxaliplatin, and trastuzumab was initiated. Although the size of metastatic lesions was reduced after six courses of treatment, a part of the primary site of gastric tumor rapidly. Pathological rebiopsy of the primary site suggested a neuroendocrine carcinoma, and he was finally diagnosed with gastric MiNEN after total gastrectomy. Thus, second-line chemotherapy was then initiated showing good response. We herein report a case of MiNEN with a rare diagnostic process.