Figure 1.

This textbook nodular/desmoplastic medulloblastoma contains nodules (A,B), in which neurocytic cells are set against a fibrillary background. Internodular regions are desmoplastic (C, reticulin preparation), and harbor cells with more nuclear pleomorphism and a higher mitotic count than intranodular cells. The border around nodules is usually sharp, but cells with an internodular phenotype can occasionally spill into nodules (D) making the border around nodules somewhat indisctinct. Differentiation along neuronal lines accompanies the neurocytic morphophenotype of intranodular cells (E, NEU‐N antibody). The growth fraction of nodules, as assessed by Ki‐67 immunolabeling, is much less than in internodular regions (F, MIB‐1 antibody). The MBEN is characterized by large nodules (G), and contrasts with the paucinodular medulloblastoma (H), in which nodules were hard to discern without the use of a reticulin preparation.