Endocrine System

This tumor is separated from the pancreas by a thin collagenous capsule. A few normal islets are seen in the pancreas at the right (arrows) for comparison.
Islet cell adenoma

Higher magnification of the previous photo. The islet cell adenoma at the left contrasts with the normal pancreas with islets at the right. Some of these adenomas function. Those that produce insulin may lead to hypoglycemia. Those that produce gastrin may lead to multiple gastric and duodenal ulcerations (Zollinger-Ellison syndrome).
Islet cell adenoma

A: The neoplastic cells are monotonous and demonstrate minimal pleomorphism or mitotic activity (H&E stain). B: Immunoreactivity for insulin confirms the neoplasm is an insulinoma. Clinically, the patient had episodic hypoglycemia.
Pancreatic endocrine tumor ("islet cell tumor") (insulinoma)