Serotonin-producing neuroendocrine tumor of pancreas

A rare functioning neuroendocrine tumor of pancreas characterized by a typically well-differentiated neoplasm composed of cells expressing serotonin. Patients may present with atypical carcinoid syndrome with abdominal pain, diarrhea, weight loss, and/or flushing. Carcinoid syndrome is usually present only when there are liver metastases. The tumors tend to be larger than non-functioning tumors and are associated with a poorer prognosis because they are almost always metastatic.