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brain cancer
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What is brain cancer?
Brain cancer refers to various tumors involving different brain cell types, characterized by the uncontrolled growth of cells in the brain. The causes of different brain cancers are mostly unknown, but identified risk factors include family history of cancer, exposure to ionizing radiation, and suppression of the immune system.
Symptoms vary based on the tumor's location, affecting functions controlled by nearby brain regions. Changes or difficulty in speech, motor functions, vision, or hearing can indicate a brain tumor. Headaches and seizures are also associated with brain cancers, as well as nausea, vomiting, or numbness in areas of the body.
Diagnosis involves neurological exams and imaging like CT scans and MRIs. A definitive diagnosis usually requires analysis of removed brain tissue. Treatment options include surgery, radiation therapy, or chemotherapy, but complete cure is often unattainable.
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How does brain cancer affect the brain?
Brain cancer refers to the uncontrolled growth of cells in the brain, with various types affecting different brain cell types. As a tumor grows, it can compress or replace brain tissue, impairing the function of the affected area and potentially causing epileptic seizures. Tumors can also indirectly impact the brain by raising intracranial pressure, especially when they develop within or compress the ventricular system. Symptoms of brain cancer can vary widely based on the tumor's location. These may include changes in speech, hearing, vision, or motor functions, as well as persistent headaches, nausea, vomiting, or numbness.
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What causes cells in the brain to become cancerous?
Brain cancer arises from a combination of factors that disrupt normal cell growth and division. While the exact causes are often unknown, key risk factors include exposure to ionizing radiation and a suppressed immune system.
Genetic mutations play a significant role. Tumor suppressor genes normally regulate cell growth, but damage to these genes can lead to uncontrolled proliferation. Similarly, proto-oncogenes, which promote cell growth, can mutate into oncogenes, driving cancerous development.
Most cancers are sporadic, resulting from new mutations, but some are familial, involving inherited genetic defects. Environmental factors and inherited susceptibilities can also contribute.
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What are the main types of brain cancer?
Brain tumors are abnormal growths that can be either malignant (cancerous) or benign. Malignant brain tumors are more common, with gliomas being the most frequent type. Gliomas originate from neuroglial cells and include astrocytomas, ependymomas, and oligodendrogliomas. Glioblastoma is the most aggressive primary brain tumor.
Diagnosis involves neurological exams and imaging like MRI and CT scans. Classification of brain tumors is based on cell type, location, grade, and genetic defects, which helps determine treatment and prognosis. Treatment options include surgery, radiation therapy, chemotherapy, and targeted drug therapy.
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How does brain cancer spread or grow inside the brain?
Brain cancer involves the uncontrolled growth of cells, leading to tumors that can progress rapidly or slowly, depending on the location and cell type. As a tumor grows, it can compress or replace brain tissue, impairing the function of the affected area and potentially causing seizures.
Malignant brain tumors can also raise intracranial pressure, particularly when they develop within or compress the ventricular system. While the causes of brain cancers are largely unknown, risk factors include exposure to ionizing radiation, immune system suppression, and family history of cancer. Malignant tumors originating elsewhere in the body can metastasize to the brain, often resulting in multiple tumors.
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What changes in brain tissue can be seen under a microscope in brain cancer?
Microscopic examination of brain cancer tissue reveals several changes. Cancer cells display inconsistencies in size and shape, along with misshapen internal structures like the nucleus. Genetic instability often leads to abnormal cells with giant nuclei containing excessive DNA.
During cell division (mitosis), the number of chromosomes is abnormally elevated, and the structures coordinating chromosome division are distorted. Cancer cells tend to be less differentiated than normal cells, termed anaplasia. When a malignant tumor no longer resembles its original tissue, it is considered undifferentiated or anaplastic. Gliomas, a type of brain tumor, are graded based on these microscopic features relative to normal cells.
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brain cancer, the uncontrolled growth of cells in the brain. The term brain cancer refers to any of a variety of tumours affecting different brain cell types. Depending on the location and cell type, brain cancers may progress rapidly or slowly over a period of many years. Brain cancers are often difficult to treat, and complete cure is often unattainable.
Causes and symptoms
The causes of different brain cancers remain largely unknown. However, researchers have identified several risk factors, including exposure to ionizing radiation, such as head X-rays at therapeutic doses (as opposed to diagnostic doses); suppression of the immune system, which may be associated with immunosuppressive therapy or with an immunodeficiency disorder (particularly one that is inherited); and family history of cancer. Symptoms of brain cancer vary widely depending on the location of the tumour. As the tumour grows, it might put pressure on nearby regions of the brain and thereby affect the functions controlled by those regions. Difficulty or changes in speech, hearing, vision, or motor functions can all indicate the presence of a brain tumour. Many brain tumours are initially discovered following chronic headaches, and in some cases seizures are associated with cancers of the brain. Symptoms may also include vomiting, nausea, or numbness in any part of the body.
Diagnosis and prognosis
If a brain tumour is suspected, a neurological exam is conducted to test general brain function. Further diagnosis usually utilizes imaging procedures such as X-rays, computed tomography (CT) scans, and magnetic resonance imaging (MRI). The location and stage of a tumour can also be determined with positron emission tomography (PET) scans. The blood supply feeding a tumour can be assessed by using an X-ray procedure called angiography. A definitive diagnosis usually requires removal of brain tissue for analysis; often this is done during tumour-removal surgery. In other cases, a needle biopsy guided by the images generated by CT scans or MRI may be used to access the tumour.
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Brain cancers are usually not diagnosed until symptoms have appeared, and survival rates vary widely, depending on type and location. Some are completely curable. Slow-growing cancers may progress for decades, whereas other types may be fatal within six to eight years. Average survival from some faster-growing tumours, however, averages no more than one year.
Treatment
Surgery is the most frequent approach to treating brain tumours. Such surgery may be curative for some cancers, but for others it may only relieve symptoms and prolong survival. In many cases, complete removal of the tumour is not possible.
Radiation therapy may be used to cure some brain cancers, but others do not respond to radiotherapy. Radiation generally works best with fast-growing types. Because radiation therapy typically involves X-rays, which pose a risk to healthy brain tissue, it is important to minimize exposure to the normal cells surrounding the tumour. This is accomplished by employing special procedures that focus the radiation. For instance, a device called a gamma knife, which emits a highly controllable beam of radiation, may be used. Even when radiation is localized, however, radiotherapy can cause side effects such as vomiting, diarrhea, or skin irritation. Radiation to the brain may cause scar tissue to form and potentially cause future problems. Memory loss may also occur.
Chemotherapy is used for some brain tumours, but, owing to the brain’s protective barrier, many chemotherapeutic agents cannot enter the brain from the bloodstream. Chemotherapy works best on fast-growing tumours, but it is generally not curative and causes side effects similar to radiation therapy. Both radiation therapy and chemotherapy are often used when a person’s general health or the location of the tumour prevents surgery.
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Prevention
In rare cases where a family history or a personal history of frequent head X-rays suggests an increased risk of brain cancer, regular screening by a neurologist may allow developing cancers to be detected earlier. Otherwise, no means of preventing brain tumours are known.