Brain Tumors

• Brain tumors refer to mass of abnormally growing cells in the brain.
• Brain tumors can be categorized based on the site of origin and location in the brain.
• There are four stages for brain tumors, Grade I-IV, where Grade I is the earliest and Grade IV is the latest stage.
• Primary causes of brain tumor include certain radiations, age, race, inheritance and harmful chemicals.
• Symptoms of the brain tumor vary according to the type of tumor and generally include headaches, nausea and confusion.  
• Brain tumors are generally diagnosed through CT scan and MRI and treated through surgery, radiotherapy and chemotherapy.

INTRODUCTION

A brain tumor is accumulation of mass from growth of abnormal cells inside the brain. The human body undergoes a natural process of growth and death of various cells all over the body including the brain.

When this normal process is disrupted, it causes excessive growth of brain cells without the corresponding death of old cells. As a result, the cells continue to accumulate causing a tumor in the brain (Tonse et al. 2018). 

This article covers the various types, stages and causes of brain tumors before discussing the symptoms and common treatments currently available. 

TYPES OF BRAIN TUMOR

Based on their origin, brain tumors are generally categorized into two main categories namely Primary tumors and Secondary tumors. 

Primary Tumors

In a primary brain tumor, the origin of the tumor is within the brain and can develop from brain cells, nerves, membranes or glands which exist inside the skull. Primary tumors may be benign or malignant. 

Benign primary tumors

Most of the primary tumors are benign i.e. they do not spread to surrounding tissues and are not aggressive. Benign tumors have a particular border and these tumor cells do not spread to other parts of the body. These tumors can usually be removed and they do not grow back. 

Malignant primary tumors

Malignant tumors can spread to other parts of the brain. These tumors may also break from site of origin and reach other parts of the body. These tumors pose a more serious threat to life as compared to benign tumors.  

Secondary Tumor

On the contrary, in a secondary tumor, the origin is from a dysfunction in any other part of the body which then extends to the brain. This may include lungs, kidney, breast and skin cancer etc.

Secondary tumors contains the same kind of cells that are present in the original cancer For instance, if secondary tumor originated in lung, the secondary tumor in brain will have lung cancer cells (Relling et al. 1999). 

Brain tumors are also named based on the type of cells they originate from and / or their location in the brain. Most common brain tumors are:

Gliomas: Glioma tumors arise from glial cells in the brain. Glial cells provide nutrients and energy to the nerve cells and aid in maintaining the blood brain barrier. Various types of glial cells include astrocytes, oligodendrocytes, microglia and ependymal cells and tumors of these cells are called as astrocytoma, oligodendroglioma, microglioma and ependymoma, respectively (Guadagno et al. 2018).  

Pituitary tumors: Tumors of the pituitary gland vary in size and behavior. Various types of pituitary tumors cause overproduction of pituitary hormones that disturb normal functioning of the body. Types of pituitary tumors include pituitary adenoma, pituitary carcinoma, craniopharyngioma and Rathke’s cleft cyst.

Pineal Tumors: These tumors occur in pineal gland that is located deep inside the brain. Pineal tumors obstruct the cerebrospinal fluid (CSF) pathways that need to be treated with surgery to create alternative path for CSF that is accumulated in the brain. Types of pineal tumors include pineocytoma, pineal cysts, germinoma etc. (Waqar et al. 2019).

Primitive neuroectodermal tumors (PNETs): These tumors are highly malignant tumors that contain small round cells having neuroectodermal origin. PNETs include medulloblastoma, ependymoblastoma and pineoblastoma and ependymoblastoma and pineoblastoma.

STAGES OF BRAIN TUMOR

There are four stages of brain tumors and are classified as Grade I - IV:

Grade I is a very early stage where the tumors are slow growing and there is a low chance of growth. 

Grade II tumors are also less likely to grow but have a possibility to spread to nearby tissues and to come back once treated. 

Grade III tumors are significantly abnormal from healthy cells, growing quickly and can spread rapidly to other parts of the brain.

Grade IV stage tumors are actively growing having their own blood vessel growth with certain dead cells at their core. 

CAUSES OF BRAIN TUMOR

Tumors occur when cells acquire mutations (errors) in their DNA. Due to these mutations cells keep dividing even at the stages when they would normally die. The cause of brain tumors and the associated changes in the cell reproduction system is still not very clear.

However, various risk factors have been identified by doctors and scientists that explain the growth of brain tumors. Among the major factors are:

Exposure to radiation: Excessive exposure of radiations like X-rays can result in abnormal mutations of the cells and increases the chances of contracting a brain tumor.

Age: Although brain tumor can occur at any age, the chances of brain tumor increase with increasing age.

Race: Brain tumors are more common among Caucasians.

Inheritance: Family history of brain tumors which results in inheritance of the tumor.

Exposure to harmful chemicals: Exposure to certain chemicals like benzene, vinyl chloride, arsenic etc. increase the risk of various types of cancers including brain tumors (McNeill, 2016). 

SYMPTOMS OF BRAIN TUMOR

Since brain plays a significant role in controlling almost all parts of the human body, an abnormality in the brain can be felt throughout the body. Among the common indication of a growing brain tumor are headaches, seizures, memory problems, nausea, confusion, hand tremors, tingling in legs and arms, sleeping problems and even inability to walk and perform daily activities.

The extent of these symptoms depends directly on location and stage of the tumor. For instance, presence of tumor on places where it can put pressure on the brain tissue produces noticeable symptoms. Pituitary gland is responsible for the release for various important hormones involved in growth and reproduction.

Tumors in pituitary gland produce symptoms like enlargement of hands and feet, increased body hair, lack of menstruation in women and low blood pressure etc. Therefore, symptoms largely vary according to the type of the brain tumor (Armstrong et al. 2015). 

DIAGNOSIS OF BRAIN TUMOR 

Brain tumors may be diagnosed through neurological exams, computerized tomography (CT) scan and/or magnetic resonance imaging (MRI). Often more complicated techniques like spinal tap or biopsies may also be required to diagnose brain tumors.

During a neurological exam, the doctor examines the hearing, vision, reflexes and coordination of the patient. Additionally, any physical signs like swelling of eyes are also examined. During MRI, a dye is injected into the blood vessels followed by an MRI scan that takes pictures of different brain areas to identify the presence of a tumor (Cha, 2004.

CT scans and angiograms are also performed by injection of a dye into the blood vessels but the imaging is done in the presence of X-rays. During a spinal tap, a small amount of CSF is removed from the lower part of the spinal cord. The patient is generally under local anesthesia during this diagnostic test that takes about 30 min. CSF is examined in the laboratory for any infection or cancer cells.

The most confirmatory diagnostic test for brain tumor is biopsy during which the doctor takes out the sample of tumor and it is observed under a microscope to identify the type and stage of cancer. Often biopsies are done as a part of treatment where they are used to remove the tumor mass completely followed by its analysis (Tempany et al. 2015).      

TREATMENT OF BRAIN TUMOR

Treatment of a brain tumor depends on the stage at which it is identified. 

Surgery: The most common treatment is through surgery whereby a specialist doctor attempts to physically remove tumor from the brain. This can be either full or partial removal depending on surrounding areas to which the tumor is attached without damaging the brain tissues.

Radiotherapy: Radiotherapy is another common method to destroy the tumors, where by high-powered rays are directed at the tumor to kill the cancerous cells and stop them from growing. 

Chemotherapy:Chemotherapy is also used to kill cancerous cells through the use of medication over a period of time.

A combination of all three methods may also be required to effectively destroy the tumor and prevent it from growing again. In a recent study, scientists have found that cancer immunotherapies can be administered directly to the brain tumors.

They found that nano-based immunotherapeutic crossed the blood brain barrier in laboratory mice. As a result of this direct drug administration, brain tumors in mice stopped multiplying thereby increasing the survival rates. 

CONCLUSION

It is concluded that the brain tumors include a plethora of types depending on their location and particular location in the brain. Exposure to harmful radiation and chemicals should be avoided to prevent the incidence of brain tumors.

People having a strong family history of cancers and above 60 years of age should consult doctors for suitable tests to diagnose cancer at early stages.      

REFERENCES

• Armstrong, T.S., Vera-Bolanos, E., Acquaye, A.A., Gilbert, M.R., Ladha, H. and Mendoza, T., 2015. The symptom burden of primary brain tumors: evidence for a core set of tumor-and treatment-related symptoms. Neuro-oncology, 18(2), pp.252-260.
• Cha, S., 2004. Perfusion MR imaging of brain tumors. Topics in Magnetic Resonance Imaging, 15(5), pp.279-289.
• Guadagno, E., Presta, I., Maisano, D., Donato, A., Pirrone, C.K., Cardillo, G., Corrado, S.D., Mignogna, C., Mancuso, T., Donato, G. and Del Basso De Caro, M., 2018. Role of macrophages in brain tumor growth and progression. International journal of molecular sciences, 19(4), p.1005.
• McNeill, K.A., 2016. Epidemiology of brain tumors. Neurologic clinics, 34(4), pp.981-998.
• Relling, M.V., Rubnitz, J.E., Rivera, G.K., Boyett, J.M., Hancock, M.L., Felix, C.A., Kun, L.E., Walter, A.W., Evans, W.E. and Pui, C.H., 1999. High incidence of secondary brain tumours after radiotherapy and antimetabolites. The Lancet, 354(9172), pp.34-39.
• Tempany, C.M., Jayender, J., Kapur, T., Bueno, R., Golby, A., Agar, N. and Jolesz, F.A., 2015. Multimodal imaging for improved diagnosis and treatment of cancers. Cancer, 121(6), pp.817-827.
• Tonse, R., Gupta, T., Epari, S., Shastri, J.G., Gurav, M., Bano, N. and Jalali, R., 2018. Impact of WHO 2016 update of brain tumor classification, molecular markers and clinical outcomes in pleomorphic xanthoastrocytoma. Journal of neuro-oncology, 136(2), pp.343-350.
• Waqar, M., Mills, S., Mallucci, C.L. and Jenkinson, M.D., 2019. Pineal tumours. Oxford Textbook of Neurological Surgery, p.427.