Department of Pathology, University of Oklahoma Health Sciences Center

Medulloblastoma (WHO Grade IV/IV)

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• Panel A: Medulloblastoma arise with the posterior fossa. In this particular case, the tumor filled and expanded the 4th ventricle (IV).
• Panel B: Medulloblastoma often lead to obstruction of the flow of cerebral spinal fluid (CSF) and lead to hydrocephalus.
• Panel C: Medulloblastoma has a high tendendy to disseminate throught the brain and spinal cord. The tumor cells are illustrated by the arrow. Therefore, treatment for medulloblastoma usually includes irradiation of the entire brain and spinal cord.

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• Panel A: Medulloblastoma is typically a densely packed, highly cellular small blue cells neoplasm with small and hyperchromatic nuclei. In contrast to medulloepithelioma, the tumor cells arrange in solid sheets without forming any specific pattern. This pattern is more reminiscent of the early but not earliest stage of embryonal development of the central nervous system.  Occasionally, Homer Wright rossettes can be seen in medulloblastomas. Mitotic activity is very brisk and many apoptotic bodies are also present. 
• Panel B: The cell boundaries between different cells cannot be distinguish in medulloblastoma cells. The cytoplasm often appear slightly fibrillary and they are called neuropils.
• Panel C: The morphologic features of medulloblastomas is that of a small blue cell tumor without significant morphologic details for classification. At the molecular level, expression of markers suggestive of certain lineage of differentiation can be detected by immunohistochemistry. In this photo, the tumor strongly express (brown stain) synaptophysin, a protein that is associated with neuroendocrine differentiation. Medulloblastomas also often express other markers that is associated with neuronal and glial differentiation.

For Comment: KarMing-Fung@ouhsc.edu