Oncology. Brain tumors arise from the uncontrolled proliferation of cells within the brain. Brain neoplasms are subdivided into primary (originating from brain tissue) and secondary (i.e., metastatic) forms. Primary brain tumors can be benign or malignant (brain cancer). Brain tumors are classified by histologic type (e.g., astrocytoma, glioma, glioblastoma, meningioma and medulloblastoma).