pathology_of_human_tumor: h&e stained sections show a heterogeneous "small round blue cell" neoplasm. in many areas the cells have dense, hyperchromatic, irregularly shaped nuclei with scant amounts of light pink cytoplasm. there is moderate mitotic activity. focally, the neoplasm is growing in sheets and small nests. much of the tumor contains a rich neuropil background and ganglion cell differentiation is easily identified occasionally binucleated ganglion cells are noted. only very focal frank nodule formation is apparent. immunoperoxidase staining for ini-1 shows diffuse nuclear expression. some areas of the tumor have marked neuronal differentiation with easily identified ganglion cells. neuropil is moderately abundant.