Questions and Answers


1. What is a brain tumour?


A brain tumour is an abnormal mass of tissue in which the cells grow and multiply without restraint, apparently unregulated by the mechanisms that control normal cells. One factor that distinguishes brain tumours from other tumours is that they arise in the skull, an organ encased by bone, and there is very little room for expansion with the skull. They are also among the few types of tumours that generally do not tend to metastasise or spread to other parts of the body. Whereas certain brain tumours occur almost exclusively during childhood and adolescence, others are predominantly tumours of adult life. The patient's age appears to correlate with the site where some tumours develop in the brain. Although most primary tumours attack member of both sexes with equal frequency, some, such as meningiomas, occur more frequently in women, while others, such as medulloblastomas, more commonly afflict boys ond young men. The prognosis for patients with a brain tumour is as individual as the patients themselves. Your doctors will help you understand the possible consequences of your specific tumour.


2. What is the difference between a primary brain tumour and a metastatic (secondary) brain tumour?


Primary brain tumours arise from the brain itself. The tumour cells do not travel to the brain from other parts of the body and, in most cases, primary brain tumour cells do not travel to other parts of the body either. The most common exception to this rule is the primary brain tumour of childhood called medulloblastoma, which can spread to the lymph nodes, bone marrow, lungs or other parts of the body. But even in this case, it is unusual for mebulloblastoma to spread outside the nervous system.


Pathologists classify primary brain tumours into two groups: the gliomas, composed of "glial" cells that invade the neural tissue surrounding them; and the nonglial tumours, which are not composed of glial cells and compress, rather than invade, the neighbouring brain as they grow. Metastatic (secondary) brain tumours will have spread to the brain from another part of the body. They most often metastasise from tumours of the lung or breast but almost any tumour can spread to the brain. They arise when abnormal cells that developed elsewhere in the body are carried to the brain by the blood flow. Metastatic tumours are the most common form of brain tumour, considerably outnumbering primary brain tumours by about 100,000 new cases each yeor.


3. What is the difference between a benign brain tumour and a malignant brain tumour?


Benign brain tumours do exist, and often can be cured with surgery alone. Some primary brain tumours are called benign because their rate of growth is so slow that many yeors may pass before the tumour grows large enough to compress functional areas of the brain, causing symptoms that require treatment. Others are considered benign because - once the tumour is diagnosed and treated - in many cases, the patient will be cured and live a normal life span and in many others, the tumour will not grow back for many years or even decades. We use the term benign with caution, however. Even a benign brain tumour may cause intolerable symptoms or may not be controllable because of its particular location in the brain.


A tumour in the brain stem or the spinal cord, for example, is often impossible to remove with surgery. In those particular locations even a small amount of tumour growth can compress and cause very serious damage to brain or spinal structures that control functions critical to life. While such a tumour may be called "benign" because of its slow growth, the situation is far from benign. We are not certain why, but some benign brain tumours may change over time to become malignant. The meningioma, for instance, is one type of primary brain tumour that can be cured, either with surgery alone or sometimes with surgery and radiation therapy. In such cases, meningioma is considered a benign tumour. But in rare cases, even a meningioma may have invasive features, which the pathologist can see in the tumourŐs cells under the microscope and which suggest that the tumour may behave more aggressively than usual. In such a case, the meningioma may not be curable. It may continue to grow despite surgery, irradiation.