Lymph Node Metastasis of Mixed Adenoneuroendocrine Carcinoma after Curative Resection Using the Expanded Criteria for Early Gastric Cancer

Endoscopic submucosal dissection (ESD) of lesions using expanded indications for early gastric cancer (EGC) has been accepted as an alternative treatment for cases without lymph node metastasis. We herein report a rare case of metastatic lymph node tissue in mixed adenoneuroendocrine carcinoma (MANEC) after curative ESD using the expanded pathological criteria. A 70-year-old man underwent ESD for two EGC lesions. A pathological examination revealed lesions that required curative resection based on the expanded pathological criteria of the Japanese classification of gastric carcinoma. However, lymph node metastasis was detected at 26 months after ESD. Additional surgical resection was performed and MANEC was pathologically diagnosed in the metastatic lymph node. The patient subsequently underwent additional chemotherapy and remains alive at 2 years after surgery. Even though MANEC is a rare tumor, this case suggests that periodic follow-up is important when patients undergo curative resection by ESD based on the expanded indications because of the high malignant potential and the poor prognosis.