For which one of the following tumors Gastrin is a biochemical marker?

Gastrin is secreted by Gastrinomas, which are neuroendocrine tumors most commonly found in duodenum. Gastrinoma:- Type of pancreatic Neuro endocrine tumor(PNET) Patient with MEN I syndrome have more chance of developing gastrinoma. -Other neuroendocrine tumor is carcinoid tumor. -Marker of medullary carcinoma of thyroid is calcitonin and GIST is CD117 (c-kit) -GIST- Mesenchymal tumor.