Somatostatinoma of the rectum.

We report a case of a 29-yr-old man with a rectal carcinoid that metastasized to the liver, secreting somatostatin. The patient first presented with an abdominal mass and mild diabetes, and, subsequently, rectal tumor and hypersomatostatinemia. Microscopic examination of the rectal tumor showed characteristic features of carcinoid. Multiple liver metastases were recognized. The plasma level of somatostatin was remarkably high (2,839 pg/ml). Plasma gut glucagon and pancreatic polypeptide (PP) increased with progress of the disease. He died of hepatic failure 20 months after his first admission. Immunoperoxidase staining showed that rectal tumor cells contained somatostatin-like-immunoreactivity. Electron microscopy of tumor tissue showed neurosecretory (D-cell) granules. Somatostatin content of the rectal tumor was very high (5,629 pg/mg).