DEFINITION

Central nervous system (CNS) malignancies refer to a heterogeneous group of cancers of the brain and spinal cord. These cancers originate from neural tissue (considered primary brain tumors) or other nonneural tissue or they can be metastatic tumors. This section provides a general overview and the following sections will address specific adult CNS malignancies in more detail.

INCIDENCE

The Central Brain Tumor Registry of the United States estimated 43,800 new cases of primary nonmalignant and malignant CNS tumors to be diagnosed in 2005. An additional 170,000 cases of metastatic brain tumors will be diagnosed. The American Cancer Society predicts that 20,500 new cases of malignant brain and central nervous system tumors will be diagnosed in the United States in 2007. The age of onset and male/female predisposition vary significantly on the basis of tumor type. For example, the average age of onset is 62 years for glioblastoma and meningioma and 16 years for medulloblastoma. The figure below shows the incidence of primary brain tumors by major histological types.

ETIOLOGY AND RISK FACTORS

There is no known cause for brain tumors; however, the following are considered risk factors:

Distribution of Central Nervous System Tumors by Histological Type.

From Central Brain Tumor Registry of the United States. (2005). Statistical report: primary brain tumors in the United States, 1998-2002 (p. 18). CBTRUS.

SIGNS AND SYMPTOMS

General signs and symptoms that are related to increased mass in the cranial vault and increased intracranial pressure include headache, nausea, vomiting, altered level of consciousness, and seizures. The individual sections will outline signs and symptoms specific to the tumor type. Focal signs and symptoms related to tumor location include seizures, weakness, sensory changes, personality changes, and endocrine abnormalities (see table below).

DIAGNOSTIC WORKUP

HISTOLOGY

Brain tumors are classified according to the World Health Organization Classification of Central Nervous System Tumors, which incorporates morphologic features, cytogenetics, molecular genetics, and immunologic markers. Malignancy is established on the basis of histological features. (See box at right.)

CLINICAL STAGING

Because of the very low incidence of metastases, not all CNS tumors require staging. In CNS malignancies staging involves imaging of the spine and obtaining cerebrospinal fluid to identify evidence of metastasis.

TREATMENT

Treatment varies on the basis of tumor type but includes surgery, radiation, and chemotherapy. The following sections will outline specific treatment dependent on tumor type. Concomitant medications used in brain tumors often include steroids, specifically dexamethasone for control of cerebral edema or symptom management, and anticonvulsants for patients who are in the acute postoperative period or who have seizures.

Brain Lobe Function and Associated Symptoms on the Basis of Lesion Location

PROGNOSIS

Prognosis is variable and depends on the tumor type.

DEFINITION

Astrocytomas are the most common type of gliomas; they arise from astrocytes (the star-shaped supporting cells for the neurons). Astrocytomas make up about half of all primary brain tumors. Astrocytomas are classified by grade according to level of malignancy according to World Health Organization (WHO) criteria.

INCIDENCE

WHO grade I astrocytomas are most common in children and young adults. They include pilocytic astrocytoma and subependymal giant cell astrocytoma.

ETIOLOGY AND RISK FACTORS

There is no known cause for brain tumors; however the following are considered risk factors:

SIGNS AND SYMPTOMS

Signs and symptoms are location dependent (see the table on page 41 in the Central Nervous System Malignancies Overview section). Because of the slow-growing nature of these tumors, symptoms may be subtle.

DIAGNOSTIC WORKUP

HISTOLOGY AND CLINICAL STAGING

WHO grade I lesions are those with low proliferative potential that are frequently discrete in nature, and cure is possible with surgical resection alone. Because of the very low incidence of metastasis, staging is not usually done with this tumor type.

TREATMENT

PROGNOSIS

With complete resection, prognosis is excellent.

DEFINITION

Astrocytomas are the most common type of gliomas; they arise from astrocytes (the star-shaped supporting cells for the neurons). Astrocytomas make up about half of all primary brain tumors. Astrocytomas are classified by grade according to level of malignancy by use of World Health Organization (WHO) criteria. WHO grade II astrocytomas are also referred to as low-grade astrocytomas or astrocytomas.

INCIDENCE

WHO grade II astrocytomas, also known simply as astrocytomas or low-grade astrocytomas, make up 26% of all primary glial tumors. They most commonly occur between 20 and 50 years of age. The median age at diagnosis is 37 years.

ETIOLOGY AND RISK FACTORS

There is no known cause for brain tumors; however, the following are considered risk factors:

SIGNS AND SYMPTOMS

Seizures are the most common presenting symptom, but there may also be headaches or focal neurological deficits (see the table on page 41 in the Central Nervous System Malignancies Overview section).

DIAGNOSTIC WORKUP

HISTOLOGY

WHO grade II astrocytomas are generally infiltrating and low in mitotic activity but tend to recur. They consist of uniform cells, showing increased cellularity and minimal pleomorphism. They are composed of well-differentiated fibrillary or gemistocytic neoplastic astrocytes. Three histologic variants include: fibrillary astrocytoma, gemistocytic astrocytoma, and protoplasmic astrocytoma. Some of these tumor types tend to progress to higher grades of malignancy.

CLINICAL STAGING

Because of the very low incidence of metastasis, staging is not usually done with this tumor type.

TREATMENT

PROGNOSIS

Median survival is 4.7 years. Eighty percent of patients survive 2 years, 46% survive 5 years, and 17% survive 10 years. Median survival at recurrence is 16 months. Prognosis is better for patients under 40 years of age at diagnosis, with a positive seizure history and absence of enhancement. It is now thought that mutation or deletion of the p53 gene is a negative prognostic indicator and, conversely, that vascular endothelial growth factor expression correlates positively with survival.

DEFINITION

Astrocytomas are the most common type of gliomas; they arise from astrocytes (the star-shaped supporting cells for the neurons). Astrocytomas make up about half of all primary brain tumors. Astrocytomas are classified by grade according to level of malignancy by use of World Health Organization (WHO) criteria. WHO grade III astrocytomas are also referred to as anaplastic astrocytomas.

INCIDENCE

This astrocytic tumor type is faster growing than a grade II astrocytoma and is considered “malignant.” Grade III astrocytomas or anaplastic astrocytomas commonly occur in patients between 30 and 50 years of age. The mean age at diagnosis is 45 years. They are slightly more common in men than women and make up 4% of all brain tumors.

ETIOLOGY AND RISK FACTORS

There is no known cause for brain tumors; however, the following are considered risk factors:

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