Figure 5 Histopathological findings of the resected specimens(A) The tumor was composed of eosinophilic and basophilic cells, and had a fibrous capsule (HE stain, low-power field). (B) The tumor shows a trabecular or alveolar (Zellballen) architecture, with nests separated by peripheral capillaries (white arrow). The cells showed pleomorphism, and the cytoplasm showed finely granular, amphophilic staining with a range from basophilic to acidophilic (HE stain, high-power field). (C) The center part of the tumor was massively necrotizing (HE stain, high-power field). (D) Tumor cells were strongly positive for chromogranin A, which is a highly useful marker of neuroendocrine granules. (Immunohistochemistry, high-power field). (E) Tumor cells were also strongly positive for synaptophysin (Immunohistochemistry, high-power field). (F) Ki-67 index was < 1% (immunohistochemistry, high-power field).