[Carcinoid of ectopic pancreas tissue--islet cell tumor]

A case of islet cell tumor--carcinoid of the ectopic pancreas is reported. The patient had been operated six times because of recurrent abdominal tumor mass and intermittent hypoglycemic coma. The first five operations were done with the diagnosis of mesotheliosarcoma by pathology. The last operation was done in our hospital with the final diagnosis of carcinoid--islet cell tumor. In addition to the light microscopic view, several diagnostic features were observed as follows: Under electron microscopy, membrane bound secretive granules were present in the tumor cytoplasm. Neither brush-like microvilli nor lumen formation of the mesothelioma were found. By immunohistochemistry, positive granules to immunoperoxidase stain of insulin were observed in some tumor cytoplasm. By laboratory test, levels of blood 5-hydroxytryptamine and urinary 5-hydroxyindolacetic acid were elevated. Sometimes it is difficult to differentiate carcinoid from islet cell tumor only by morphology, because both are derived from the same origin during the embryonic development which is probably related to the endocrine system from the embryonic foregut. The latter arises from the neuro-ectoderm and belongs to APUD system.