Gastric Neuroendocrine Tumors

Gastric neuroendocrine tumors (GNETs) are neoplasms arising from enterochromaffin-like cells within the gastric mucosa. These tumors represent <1% of all gastric neoplasms but are increasingly diagnosed due to the widespread use of upper endoscopy. GNETs are classified into 3 main subtypes based on their pathophysiology, clinical behavior, and association with hypergastrinemia: type 1, type 2, and type 3. Type 1 GNETs, the most common subtype, occur in the setting of chronic atrophic gastritis and hypergastrinemia, leading to hyperplasia of enterochromaffin-like cells. These tumors are typically small, multifocal, and have a low risk of metastasis. Type 2 GNETs are associated with Zollinger-Ellison syndrome (ZES) and multiple endocrine neoplasia type 1 (MEN1), driven by excessive gastrin secretion from gastrinomas. They have a variable clinical course and a slightly higher metastatic potential than type 1. In contrast, type 3 GNETs are sporadic, gastrin-independent, and more aggressive, often presenting as solitary, large tumors with a significant risk of metastasis. GNETs are diagnosed using a combination of endoscopic evaluation, histopathology, and biochemical markers, including serum gastrin levels and chromogranin A. Endoscopic ultrasound (EUS) and cross-sectional imaging help assess tumor invasion and metastatic spread. Management strategies depend on tumor type, size, grade, and metastatic potential. Type 1 and select type 2 GNETs may be managed with surveillance or endoscopic resection, while type 3 GNETs often require aggressive surgical intervention and, in some cases, systemic therapy. Given their heterogeneous nature, GNETs require an interprofessional approach to optimize diagnosis, treatment, and long-term surveillance. Understanding their classification, pathogenesis, and therapeutic options is crucial for improving patient outcomes and guiding evidence-based management strategies.