Figure 3.

One biphasic medulloblastoma was characterized by extensive regions of neurocytic differentiation (A), in which the cell density was low and ganglion cells were occasionally found. The tumor lacked internodular desmoplasia (B, reticulin preparation). In some regions of this tumor, islands of undifferentiated cells (C), with a high mitotic count and Ki‐67 immunolabeling index (D, MIB‐1 antibody), tended to occur around small blood vessels, but were in turn surrounded by a concentric arrangement of neurocytic cells and hypocellular neurofibrillary areas (C).