A, Sagittal view of noncontrast abdominal MRI showing a hypointense lesion in the head of the pancreas. B, EUS showing a 1.6-cm × 1.0-cm lesion in the head of the pancreas. C, Photomicrograph showing the typical histology of an islet cell tumor with nests and festooning bands of cells with islet cell morphology. Scale bar represents 50 microns. D, This Ki-67 immunohistochemical stain documents the elevated proliferation index of this intermediate-grade tumor.