Primary and secondary (metastatic) malignant tumors that occur in the cerebellum. histologic types include medulloblastomas, high grade (who stage iii or iv) cerebellar astrocytomas, lymphomas, gangliogliomas, gliosarcomas, and several other subtypes. the most frequent malignant cerebellar neoplasm of childhood is medulloblastoma. in adults, metastases from other sites are relatively common. clinical features include ataxia, headache, nausea, dizziness, nystagmus, diplopia, papilledema, etc.