Islet cell tumors

Abstract

Although quite rare, the islet cell tumors present an important challenge to the clinician because of their protean manifestations and potential lethality. Early diagnosis is essential and depends on recognition of the classic and variant clinical syndromes followed by confirmation of elevated peptide levels by radioimmunoassay. Medical control of the hormonal syndrome with agents such as diazoxide for insulinoma, omeprazole for gastrinoma, and octreotide for vipoma and glucagonoma allows an orderly and thorough investigation for associated endoerinopathies and comorbid medical conditions. Localization and staging of the tumors are important because they may be small and occult, widely metastatic, or multifocal in the context of multiple endocrine neoplasia type I (MEN I) syndrome. Computed tomography, visceral angiography, endoscopic ultrasonography, and indium-labeled octreotide scanning are the most useful preoperative imaging techniques. Surgical exploration that includes intraoperative ultrasonography remains an essential localization technique for occult tumors, particularly insulinomas and gastrinomas. For all patients other than some with advanced metastatic disease or MEN I syndrome, an aggressive surgical approach with the intent of complete and curative tumor excision is indicated. Surgical cure is possible in most insulinomas, a substantial proportion of gastrinomas, and some patients with the other more rare and malignant islet cell tumors. At present, adjuvant medical therapies for unresectable malignant disease have limited efficacy. However, a variety of newer and innovative tumor localization techniques, operative strategies, and nonoperative treatment modalities hold considerable promise for the attainment of higher cure rates and improved palliation.