Gastric Carcinoid Tumors

Gastric carcinoids comprise less than 1% of gastric neoplasms. They can be separated into three distinct groups based on both clinical and histologic characteristics: type I: those associated with chronic atrophic gastritis type A (CAG-A), type II: those associated with Zollinger-Ellison (ZE) syndrome, and type III: sporadic gastric carcinoid tumors. Both type I and type II gastric carcinoids are associated with hypergastrinemia. High levels of gastrin are thought to result in hyperplasia of enterochromaffin-like cells in the gastric mucosa. These hyperplastic lesions may ultimately develop into carcinoid tumors. Both type I and type II carcinoids generally measure less than 1 cm in diameter and are often multifocal. They are generally indolent, and have been reported to metastasize in less than 10% of cases.

Type I and type II carcinoids can usually be managed successfully with endoscopic resection followed by close endoscopic surveillance. Patients with larger or recurrent tumors may require more extensive surgical resection. Antrectomy may result in normalization of serum gastrin levels, and has been reported to result in tumor regression in selected cases. Similarly, the use of somatostatin analogs has been shown to reduce gastrin levels and cause tumor regression in patients wit gastric carcinoids associated with the Zollinger-Ellison syndrome. The long-term benefits of these interventions, however, remain unclear.

Between 15-25% of gastric carcinoids are sporadic. In contrast to type I and type II carcinoids, these lesions develop in the absense of hypergastrinemia, are usually greater than 1 cm in size, and tend to pursue and aggressive clinical course. Sporadic carcinoid tumors have been associated with an atypical carcinoid syndrome, which is manifested primarily by flushing and thought to be mediated by histamine. The majority of sporadic carcinoid tumors are metastatic at the time of presentation, and death due to disease is frequent. Because of the aggressive nature of these lesions, most are treated with radical gastrectomy.

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