Table 1.

Pathologic subtypes of medulloblastoma

Pathologic subtype	Histologic appearance	Prognosis (% overall survival at 5 years)
Classic (71%)	Sheets of uniform small cells with high nuclear to cytoplasmic ratio and round hyperchromatic nuclei. Focal neural differentiation is present in a minority.	WNT subgroup (>95%) SHH subgroup (80%) Group 4 (70%)
Nodular/desmoplastic (5%) – Conventional (3%) – Paucinodular (1%) – DMEN (<1%)	Heterogeneous architecture with regions of dense intercellular reticulin and nodules containing tumor cells with a neuronal phenotype and decreased growth fraction.	Infants and children (80%) Adults (80%) p53 mutant tumors (45%)
Large cell/anaplastic (17%)	Anaplastic tumors have marked pleomorphism, nuclear molding, cell-cell wrapping, and high mitotic activity. Large cell type features spherical cells with round nuclei, open chromatin, and prominent central nucleoli. Large cell and anaplastic types coexist.	Group 3 (<50%)

Abbreviations: WNT, wingless; SHH, sonic hedgehog; DMEN, desmoplastic medulloblastoma with excessive nodularity.