Electron microscopy of neoplasms of pancreatic islet cells.

Neoplasms of pancreatic islet cells that produce widely divergent clinical syndromes cannot be distinguished from one another by conventional microscopy. Differentiation among these tumors by electron microscopy is possible in some cases only. Coordinated clinical evaluation, histochemical and ultrastructural studies, and assay of serum and neoplastic tissue for various polypeptide hormones afford the best characterization of these neoplasms.