Fig. 3

Histopathological examination. a Gross picture of the specimen. The tumor was 116×56×19 mm in diameter and occupied most of the renal pelvis. b Hematoxylin-eosin staining showed that the tumor was composed of solid nests of tumor cells (and partly of tumor cells cords) with a high nucleus-cytoplasm ratio and central necrosis. c Immunohistochemical staining showed that almost all tumor cells were positive for CD56, synaptophysin, and chromogranin. Ki67 was detected in 15–20% of the tumor cells. These features were consistent with neuroendocrine carcinoma