Gastroesophageal Junction Neuroendocrine Neoplasm

**Semantic type:** Neoplastic Process

**Definition:** A neoplasm with neuroendocrine differentiation that arises from the gastroesophageal junction. It includes neuroendocrine carcinomas (poorly differentiated neuroendocrine neoplasms) and extremely rare neuroendocrine tumors (well-differentiated neuroendocrine neoplasms).