Multihormone-producing islet cell tumor of the pancreas associated with somatostatin-immunoreactive amyloid: immunohistochemical and immunoelectron microscopic studies.

Pancreatic islet cell tumors, especially insulinomas, are often associated with amyloid deposition in the tumor tissue. Biochemical analysis has demonstrated that the amyloid protein from insulinoma is derived from islet amyloid polypeptide (or amylin) that is produced by tumor cells originating from beta cells of the islet of Langerhans. We examined a case of malignant pancreatic islet cell tumor with amyloid deposition in the tumor tissue using immunohistochemistry and double-labeling immunogold electron microscopy. The tumors were composed of cells producing multiple hormones, including somatostatin, gastrin, amylin, insulin, calcitonin gene-related polypeptide, and calcitonin. Amyloid deposits reacted with antisomatostatin antiserum but not with other antisera, including antiamylin. The present study demonstrated for the first time that amyloid associated with islet cell tumors is not always derived from amylin and can come from somatostatin.