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Cancer is characterised by the uncontrolled growth of abnormal cells in the body that can potentially spread to other areas, according to the National Cancer Institute’s definition.
This term encompasses a broad range of diseases marked by abnormalities in cell growth. Due to this uncontrolled proliferation of cells, the formation of a mass known as a tumour may occur. Of these, some tumours may be cancerous, while others are noncancerous and do not spread to other parts of the body.
Brain cancer, specifically, involves the growth of abnormal cells in the brain or spinal cord. It originates from the brain cells themselves and is typically named after the type of tissue from which it arises. Primary brain cancers develop from the cells within the brain and differ fundamentally from secondary brain cancers, which result from cancer cells that have metastasised from other parts of the body to the brain.
These growths disrupt normal brain function, potentially impacting movement, sensory perception, and cognitive abilities, making it crucial to understand their origins and characteristics.
Symptoms of brain cancer can vary significantly depending on the tumour’s size, location, and rate of growth. These symptoms could also be caused by the tumour pressing on or damaging nerves or other parts of the brain as it grows.
It’s important to note that these symptoms can also indicate other health conditions, so it’s crucial to consult a healthcare professional for a proper diagnosis.
Tumours represent an abnormal mass of cells that grow and multiply without the usual controls that regulate cellular life cycles. They can be categorised into two primary groups: benign and malignant.
Benign brain tumours are non-cancerous growths that generally grow at a slow pace and have a lower likelihood of recurrence following treatment. However, their location and size can still cause serious symptoms depending on the pressure they exert on sensitive areas of the brain.
Common types of benign brain tumours include:
Malignant brain tumours are characterised by their rapid growth and a higher risk of spreading within the brain. These tumours can be life-threatening due to their invasive nature and the complex regions of the brain they may affect.
Types of malignant brain tumours include:
Benign tumours are those that remain localised, do not spread to other parts of the body, and are generally not considered cancerous. While they might not be life-threatening, their size and location can still cause significant health issues if they compress nearby tissues or organs.
Conversely, malignant tumours are more aggressive and may invade and destroy surrounding healthy tissue. These tumours can also metastasise, meaning they can spread to other parts of the body and initiate new areas of cancer, leading to serious health implications.
In the context of the brain, these distinctions remain relevant. Brain tumours, also known as intracranial tumours, can either be categorised into two main types: benign and malignant, each presenting different growth patterns and health implications.
Understanding the causes of brain cancer requires examining how genetic predispositions and environmental influences interact intricately. Do note, however, that the process by which brain tumours develop is highly complex and not entirely understood. For instance, it remains a mystery why some individuals exposed to the same environmental conditions develop brain tumours while others do not.
In general, it is understood that when cell growth regulation fails, cells may uncontrollably divide, forming tumours. These tumours can hinder immune system recognition and produce angiogenesis factors, prompting new blood vessel growth to meet their increased oxygen and nutrient demands. This interplay of genetic faults and environmental factors fuels brain cancer development, highlighting its multifaceted origins.
Several factors could potentially cause brain tumours, including:
Genetic mutations are thought to play a crucial role in the development of brain tumours. These genetic mutations can either be inherited from parents or arise spontaneously in the body and impact the genes that control cellular growth and division. Typically, these genes are responsible for ensuring that cells grow and divide in an organised way, repair any DNA damage, and initiate cell death if the damage is too extensive. When these genes are altered, cells can start to grow uncontrollably. In some individuals, inherited genetic conditions can predispose them to these mutations, making them more susceptible to developing brain tumours. Conditions such as neurofibromatosis, Von Hippel-Lindau disease, and Li-Fraumeni syndrome are examples where genetic predispositions can lead to tumour formation.
Metastatic brain tumours, referred to as secondary brain tumours, develop when cancer cells from primary tumours elsewhere in the body spread to the brain. Cancers frequently spreading to the brain encompass lung cancer, breast cancer, melanoma, and renal cell carcinoma. This metastatic process involves cancer cells breaking away from their original site, travelling through the bloodstream or lymphatic system, and forming new tumours within the brain tissue.
Exposure to ionising radiation is another risk factor thought to cause the development of brain tumours. This can include radiation from medical treatments such as radiotherapy for other cancers and, less commonly, exposure to radiation from environmental sources. Radiation can damage DNA in brain cells and lead to mutations that disrupt normal cell functions and promote tumour growth.
Diagnosing brain tumours involves a comprehensive series of tests and procedures designed to identify the presence, type, stage, and specific characteristics of the tumour. Each diagnostic tool contributes uniquely to providing a detailed understanding of the tumour, which is crucial for planning an appropriate treatment approach.
A neurological exam is typically the first step in the diagnostic process for a suspected brain tumour. During this exam, a cancer specialist or neurologist will test functions controlled by the brain, including vision, hearing, balance, coordination, strength, and reflexes. Difficulty in any of these areas may indicate problems in specific parts of the brain, which helps narrow down the potential locations of a tumour.
CT Scan: A Computed Tomography (CT) scan is often one of the first imaging tests performed if a brain tumour is suspected. It creates cross-sectional images of the brain, which can show tumours, as well as bleeding, swelling, and other abnormalities.
MRI: Magnetic Resonance Imaging (MRI) uses magnetic fields and radio waves to produce images of the brain. MRIs can distinguish between different types of tissue, which can help with identifying the boundaries between a tumour and normal brain tissue. Special types of MRI scans, like functional MRI, magnetic resonance spectroscopy, and magnetic resonance perfusion, provide additional information about brain activity, the chemical environment within the tumour, and blood flow within the tumour, respectively.
PET Scan: Positron Emission Tomography (PET) scans are less commonly used initially but can be helpful in assessing the atypical metabolic activity of the tumour. In a PET scan, a small amount of radioactive material is injected into the bloodstream, which accumulates in cancer cells. A scanner then detects this material to produce images that highlight areas of high activity, indicative of rapidly dividing cancer cells.
Brain Biopsy: If imaging tests suggest the presence of a tumour, a brain biopsy may be conducted to check if the tumour is malignant. This can be performed as part of surgical removal of the tumour or separately using a needle. A stereotactic needle biopsy involves drilling a small hole in the skull and inserting a needle to extract a tissue sample.
While the exact cause of most brain tumours remains largely unknown, there are several recognised risk factors that could potentially increase the likelihood of developing a brain tumour.
It is thought that the development of a brain tumour generally increases with age. However, certain types of brain tumours, such as medulloblastomas, are more commonly diagnosed in children, indicating that the risk varies not only by age but also by tumour type. In Singapore, between 2016 and 2020, according to the Singapore Cancer Registry Annual Report 2020, brain and central nervous system (CNS) cancers were notably diagnosed among the younger population, with 67 males and 52 females aged 0 to 29 years being diagnosed. Interestingly, brain and CNS cancers are not listed among the top 10 cancers in individuals over 40 years old, indicating a potential influence of age on the types of cancers prevalent in different age groups.
Although less common, there are also risks associated with radiation exposure from diagnostic imaging, such as CT scans and head X-rays. These risks, however, are generally considered small and are usually outweighed by the benefits of accurately diagnosing and treating medical conditions.
A family history of brain tumours or inherited genetic syndromes such as Turner syndrome can significantly increase an individual’s risk. These conditions are known to affect cellular growth pathways, leading to an increased likelihood of tumour development.
Statistical data shows a slight variation in brain tumour incidence between genders. Some types of brain tumours are more common in males, whereas others may be more prevalent in females. For instance, according to the Singapore Cancer Registry Annual Report 2020, between 2016 and 2020, a total of 105 males between the ages of 0 and 39 were diagnosed with cancers of the brain and CNS. However, there were only 52 incident cases among females of the same age group, suggesting that biological differences between genders could influence tumour development.
Having a family member with a brain tumour can increase the risk of developing one, especially if the family member has a genetic condition associated with brain tumours. This familial tendency suggests a genetic component to susceptibility, which might be significant in a small percentage of cases.
Individuals with compromised immune systems, whether from medical conditions like HIV/AIDS or from medical treatments such as organ transplants, are at an elevated risk for developing various types of tumours, including brain tumours. Since the immune system plays a crucial role in detecting and controlling abnormal cell growth, any impairment could lead to increased tumour formation.
Grading brain tumours is crucial in assessing their severity by evaluating their cellular properties and growth potential.
The grading system spans from Grade I, indicating the least aggressive tumours, to Grade IV, denoting the most aggressive forms, guiding treatment decisions and prognosis.
Grade I brain tumours are considered benign, with cells that appear nearly normal under a microscope. These tumours grow slowly and are the least likely to invade surrounding brain tissue. They are often associated with long-term survival and are more common in children than in adults. Surgical removal of Grade I tumours could lead to a potential for a complete cure.
These tumours are also relatively slow-growing but are more likely to behave in a malignant manner compared to Grade I tumours. Under a microscope, the cells of a Grade II tumour appear slightly abnormal. There is a possibility of these tumours invading adjacent normal tissues and recurring, sometimes as a higher grade tumour.
Grade III tumours are malignant and characterised by actively reproducing abnormal cells that can infiltrate nearby normal brain tissue. Microscopically, these cells appear significantly abnormal and more aggressive than those in Grade II tumours. Grade III tumours are also prone to recurrence, often returning as more aggressive tumours.
The most aggressive form, Grade IV brain tumours, grow rapidly and spread quickly into nearby brain tissue. These tumours are highly malignant, with cells that look very abnormal under a microscope. They are known for forming new blood vessels to sustain their rapid growth and often have areas of dead cells (necrosis) at their core due to their fast growth outstripping their blood supply.
NOTE: The grade of a brain tumour can sometimes evolve over time; for instance, a lower-grade tumour can transform into a higher grade over time due to genetic changes within the tumour cells. This dynamic nature of brain tumours makes ongoing monitoring essential after initial treatment.
Since understanding the grade of a brain tumour is crucial for developing an appropriate cancer treatment plan, pathologists grade brain tumours by examining tissue obtained from a biopsy. The process involves assessing the tumour’s cellular makeup, rate of cell division, and the presence of necrosis and vascular proliferation.
It is crucial to consult a doctor if you experience symptoms that may suggest a brain tumour, such as persistent headaches, vision problems, seizures, or changes in personality. Early detection is key in managing brain tumours effectively.
Make an appointment with your healthcare provider as soon as you notice any concerning symptoms. It’s important to discuss all symptoms, even those that seem minor, as they can provide significant clues about the presence of a tumour.
Prepare for your visit by listing all symptoms, medications, and any prior medical history. You may want to consider having a family member or close friend accompany you for support and to assist in recalling the information discussed.
The doctor will likely conduct a neurological exam to assess your reflexes, muscle strength, eye and mouth movement, coordination, and alertness. Based on the initial findings, they may order additional diagnostic tests, such as an MRI or CT scan, to investigate your symptoms further. This comprehensive approach helps ensure proper diagnosis and appropriate treatment planning.
Treatment approaches for brain cancer differ depending on the tumour type, size, location, and the patient’s general health. Here are the main treatment modalities available:
