Clear Cell Islet Cell Tumor of the Pancreas: An Immunohistochemical and Ultrastructural study

ABSTRACT

A clear cell islet cell tumor of the pancreas is extremely rare and characterized by extensive clear cell components. Electron microscopic and immunohistochemical findings are essential to prove that the mass with clear cells is an unusual manifestation of an islet cell tumor. Herein, we report a case of clear cell islet cell tumor of a 54-year-old woman with abdominal pain. The tumor was composed of polygonal clear cells arranged in nests, trabeculae, and ribbon pattern with the extensively fibrous stroma. These tumor cells showed strong reactivity for chromogranin and weak reactivity for somatostatin and glucagon. An electron microscope revealed that the important contributing factor of the clear cytoplasmic change was mainly due to an accumulation of lipid droplets, coupled with cytoplasmic swelling in some areas. Some tumor cells showed many endosecretory granules ranging from 111 to 297nm in diameter. In the clinical and immunohistochemical findings these granules were consistent with somatostatin granules in morphology and size.