HER2 expression in gastrointestinal carcinoid tumors: high in intestinal but not in gastric tumors.

We investigated HER2 expression immunohistochemically in 12 patients with a gastrointestinal (GI) carcinoid tumor. The tumors were located in the stomach in three patients, the duodenum in four, the vermiform appendix in one, and the rectum in four. HER2 was highly expressed in the nine intestinal, but not in the three gastric carcinoid tumors. These findings suggest that HER2 might be highly expressed in intestinal, but not in gastric, carcinoid tumors.