Tumors

• pilocytic astrocytoma which is benign in posterior fossa of children supratentorial good prognosis

  gfap positive bipolar neoplastic cells with microcysts and rosenthal fibers ( eosinophilic cork screw fibers) solid and cystic
• medulloblastoma is malignant compresses 4th ventricle causing non communicating hydrocephalus papilledema and headaches it occurs in cerebellum and may cause truncal ataxia by affecting the vermis sends drop metastasis to the spinal cord

  homer right rosettes small blue cells surrounding central area of neuropil synaptophysin positive from pnet