The antral mucosa as a new site for endocrine tumors in multiple endocrine neoplasia type 1 and Zollinger-Ellison syndromes.

Carcinoid tumors were identified in the antro-pyloric mucosa of four patients with multiple endocrine neoplasia type 1 (MEN-1)/Zollinger-Ellison syndrome, accounting for 8.7% of 46 patients with this condition examined by endoscopy and histology. In contrast, no tumors were found in the antral biopsies from 124 cases of sporadic Zollinger-Ellison syndrome (P < 0.001), indicating a prominent role for the MEN-1 gene defects in tumor development. Immunohistochemically the tumors did not express the hormones produced by antral endocrine cells (gastrin, somatostatin, serotonin). In contrast, two of them were diffusely immunoreactive for the isoform 2 of the vesicular monoamine transporter (VMAT-2), a marker specific for the gastric nonantral enterochromaffin-like (ECL) cells. In one of these patients a second antral VMAT-2-positive carcinoid was seen 21 months after the first diagnosis. The other two antral carcinoids were unreactive for VMAT-2. Multiple ECL cell tumors were found in the gastric body-fundus mucosa of the two patients with VMAT-2-positive, but not in those with VMAT-2-negative, antral carcinoids. In one case, the former tumors were diagnosed 22 months after the detection of the antral tumor. We conclude that the antral mucosa is an additional tissue that may harbor endocrine tumors in MEN-1 syndrome. These tumors did not express the phenotype of normal antral endocrine cells and, in at least two cases, were identified as ectopic ECL cell carcinoids.