pathology_of_human_tumor: the malignant hypercellular tumor is comprised of sheets of small to intermediate sized cells that are regionally heterogeneous, partly due to cellular disassociation and geographic necrosis that includes prominent apoptosis. in many areas the neoplastic cells are small, with round to angular nuclei that contain stippled chromatin, indiscrete nucleoli and little cytoplasm in a few foci intervening neuropil is appreciated. however, in multiple regions, including perivascular accentuation, the tumor cells are enlarged and have ovoid to angular nuclei with cleared chromatin and prominent nucleoli. some cells in these foci have eccentric nuclei and a moderate amount of eosinophilic cytoplasm. nuclear molding and cellular "cannibalism" is apparent in these regions as well as increased mitotic activity. immunoperoxidase staining shows retained expression of ini-1.