Brain cancer

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A brain tumor is an intracranial growth resulting from abnormal and uncontrolled cell division. Such growths can originate within the brain (neurons, glial cells like astrocytes, oligodendrocytes, and ependymal cells), lymphatic tissue, blood vessels, cranial nerves (myelin-based Schwann cells), the brain's coverings (meninges), skull, pituitary, pineal gland, or they can spread from cancers primarily found in other parts of the body (metastatic tumors).

Incidence and Prevalence

In the United States in 2000, brain tumors accounted for approximately 16,500 new cases. This made up 1.4% of all cancers, 2.4% of all cancer fatalities, and 20–25% of pediatric cancers. Ultimately, an estimated 13,000 individuals die annually due to brain tumors.

Causes

Metastatic cancers (cancers that spread from other parts of the body) are more common than primary brain and spinal cord tumors. There's limited data on environmental factors causing brain tumors, although exposure to vinyl chloride or ionizing radiation has been implicated. Certain genetic conditions, such as Von Hippel-Lindau syndrome, multiple endocrine neoplasia, and neurofibromatosis type 2, increase the risk of brain tumors.

Classification

Primary Tumors

Primary brain tumors arise directly from cells within the brain. The distinction between benign and malignant is less clear for brain tumors than for tumors in other parts of the body. Even benign brain tumors can cause significant harm by compressing brain tissue. Common benign tumors include meningiomas (originating in the meninges), pituitary adenomas, and Schwanomas (e.g., acoustic neuroma)

Main articles: meningioma, pituitary adenoma, Schwanomas, and acoustic neuroma

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Most primary brain tumors stem from glia (gliomas), such as astrocytomas, oligodendrogliomas, and ependymomas. Mixed cell tumors like mixed gliomas or oligoastrocytomas also occur. Furthermore, there are tumors originating from both glial and neuronal cells, like gangliogliomas and disembryoplastic neuroepithelial tumors. Other primary brain tumor types include primitive neuroectodermal tumors (e.g., medulloblastoma, neuroblastoma, and retinoblastoma) and tumors of the pineal region, like pineocytoma

Main articles: astrocytoma, pilocytic astrocytoma, oligodendrogliomas, ependymoma, and glioblastoma multiforme

Main articles: mixed gliomas, oligoastrocytomas, medulloblastoma, retinoblastoma, and neuroblastoma

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Primary cerebral lymphoma, or primary CNS lymphoma, is another type of primary brain tumor. This form of non-Hodgkin's lymphoma is more common in people with severe immunosuppression, such as those with AIDS.

The World Health Organization (WHO) introduced a classification system for primary brain tumors in 1993.

Secondary Tumors and Non-Tumor Lesions

Secondary or metastatic brain tumors arise from cancers located in other body parts. Common origins include the lung, skin (malignant melanoma), kidney, breast, and colon. These cells reach the brain through the bloodstream.

Some non-tumoral lesions can mimic brain tumors. Examples include tuberculosis, cerebral abscess due to toxoplasmosis, and hamartomas.

Symptoms

Symptoms from brain tumors depend on the tumor's size and location. Many benign tumors remain symptom-free for extended periods. New-onset epileptic seizures are often an early sign of a brain tumor.

Increased intracranial pressure can lead to headaches, vomiting, altered consciousness, and other symptoms. Depending on the tumor's location and the damage it inflicts on the brain, symptoms can range from cognitive and behavioral changes to motor or sensory issues.

For example, a pituitary tumor may manifest as a hormonal imbalance. If a tumor is near the optic nerve, it can cause vision problems.

Brain Tumor Diagnosis

Brain tumors don't always present with a specific set of symptoms. However, any gradual appearance of neurological signs, symptoms indicating increased intracranial pressure, or onset of epilepsy in someone without a previous history of it should prompt concern. Conversely, a sudden appearance of symptoms, such as an unexpected epileptic seizure, or acute intracranial hypertension – possibly caused by internal tumor bleeding, brain swelling, or a blockage in the cerebrospinal fluid flow – are also potential indicators of a brain tumor.

Medical imaging is pivotal in diagnosing brain tumors. The older, invasive techniques like pneumoencephalography and cerebral angiography have now been superseded by safer, non-invasive, high-resolution techniques like computed tomography (CT) and magnetic resonance imaging (MRI). On a CT scan, benign brain tumors generally appear as hypodense masses. MRI reveals them as either hypo- or isointense on T1-weighted scans and hyperintense on T2-weighted scans. Surrounding edema (swelling) is also seen as hyperintense on T2-weighted scans. A significant number of malignant primary and metastatic brain tumors will show uptake of contrast agents on either CT or MRI. This happens because these tumors compromise the usual integrity of the blood-brain barrier, leading to enhanced permeability.

Electrophysiological tests like electroencephalography (EEG) have limited use in brain tumor diagnosis. They aren't the primary tool but can offer supplemental information in some cases.

For an unequivocal diagnosis of a brain tumor, a histological examination of tumor tissue samples is imperative. These samples are generally obtained via a brain biopsy or during an open surgical procedure. This examination not only confirms the diagnosis but also guides treatment decisions and helps predict outcomes.

Brain Tumor Treatment and Expected Outcomes

Meningiomas are often surgically removable, especially if they are not located at the skull base. However, complete removal isn't always guaranteed. For challenging cases, stereotactic radiotherapy offers a potential alternative.

Most pituitary adenomas can be excised surgically. Surgeons often use a minimally invasive route via the nasal cavity and skull base, known as the trans-nasal, trans-sphenoidal approach. Larger adenomas might require a craniotomy, a procedure that involves opening the skull. In cases where surgery isn't feasible, radiotherapy, including stereotactic techniques, becomes the preferred option.

While there isn't a universal treatment protocol for primary brain tumors, most cases consider surgical removal or cytoreduction – where the aim is to decrease the tumor volume by removing as much of it as possible. Recurrence is a challenge because these tumors can infiltrate surrounding tissues. Malignant tumors typically require both postoperative radiotherapy and chemotherapy. Even benign or "low-grade" gliomas might require radiotherapy if surgery doesn't significantly reduce the tumor size.

Factors influencing survival rates in brain tumor patients include tumor type, patient age, overall health, and the extent of tumor removal. While patients with benign gliomas can have extended survival durations, those with aggressive tumors like glioblastoma multiforme often have limited life expectancy post-diagnosis.

For metastatic tumors, surgical removal of isolated tumors followed by radiotherapy and/or chemotherapy is the typical approach. When multiple metastatic tumors are present, a combination of radiotherapy and chemotherapy is standard. However, the prognosis is largely influenced by the nature of the primary tumor, and outcomes can be unfavorable.

Helpful Resources

The Brain Tumor Foundation - Comprehensive resources for patients and their caregivers. Mayo Clinic - Detailed information on brain tumor diagnosis and treatment modalities. Brain Surgery-Neurosurgery Patient Help Site - A platform offering insights and support for neurosurgery patients.

External links

• The Brain Tumor Foundation - resources for patients and caregivers
• Mayo Clinic - Brain tumor diagnosis and treatment information
• Brain Surgery-Neurosurgery Patient Help Site

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