Brain tumors can occur in any part of the brain or spinal cord. Tumors of the brain may be primary, arising from tissues within the brain, or secondary, resulting from a metastasis from a malignant neoplasm elsewhere in the body. Secondary brain tumors are the most common type. Brain tumors are generally classified according to the tissue from which they arise. The most common primary brain tumors originate in astrocytes. These tumors are called gliomas (e.g., astrocytoma, glioblastoma multiforme) and account for 65% of primary brain tumors (Table 54-12). Glioblastoma mutiforme is the most common primary brain tumors, followed by meningioma and astrocytoma. More than half of brain tumors are malignant; they infiltrate the brain parenchyma and are not amenable to complete surgical removal. Other tumors may be histologically benign but are located such that complete removal is not possible. Brain tumors are more commonly seen in middle-aged persons, but they may occur at any age.