Endocrine tumor of the pancreas composed of argyrophil and B cells. A correlated light, immunofluorescent, and ultrastructural study.

A correlated morphological study, employing endocrine cell stains, immunofluorescence, and electron microscopy, was performed on biopsy specimens taken from a pancreatic tumor and liver metastases in a woman with hypoglycemic symptoms and high fasting insulin levels. The study revealed the tumor to be composed of two different endocrine cell populations, irrespective of the primary or metastatic growth. The first cell type fulfilled all the morphological characteristics of the islet B cells. The second was argyrophil (with the Grimelius silver method) and showed the morphological pattern of polypeptide-hormone-producing cells. With the lack of a detectable symptomatology, normal blood levels of the hormones other than insulin, and the negative results of a large number of immunofluorescence tests, we were unable to indetify the specific nature of the second type of cells.