What is cancer?
Cells are the building blocks that form different structures in the body. Genes contain the instructions in cells for making new proteins, which give every cell its specific function. These regulatory elements control how cells behave. Abnormal changes (mutations) in genes can turn normal cells into cancer cells through complex mechanisms.
Cell division is a tightly controlled mechanism in which a cell will create two daughter cells. These new cells replace injured or dying cells as needed. This duplication is controlled by several proteins, which ensure the correct progression through the cell cycle (process that the cell follows to duplicate). These proteins can be accelerators to progress through the cell cycle, or can act as brakes to provide time for the cell to correct duplication of the DNA and avoid introducing mutations. Normal cells stay where they belong and do not spread to other parts of the body; they die as they grow old, or become damaged.
A cancer cell can duplicate extensively and without control for two reasons: the accelerator protein (proto-oncogene) has a mutation which means the acceleration cannot be stopped, or the brake protein (tumour suppressor) has a mutation that does not allow them to work properly. Sometimes, both events can happen in different proteins making them difficult to treat.
Cancer cells duplicate extensively until they produce a massive amount of cells. The initial proliferative cells form a solid mass, called a primary tumour. If they continue growing and dividing, cancer cells will not stay in place, as they should. They will invade other tissues giving place to metastasis. Researchers are still learning what causes genes to mutate and cause cancer.
This is a very broad explanation of what cancer is, and it applies more to adult cancers. Most paediatric cancers develop because of sporadic epigenetic alterations. A very simple classification for paediatric cancers can be the following:
- Intracranial solid tumors
- Extracranial solid tumors
Cancer may occur anywhere in the body. Cancers are named depending on the type of cell that triggers the uncontrolled proliferation.. The uncontrolled proliferation of glial cells, originate in what scientists call glioma.
Paediatric brain tumours
Brain and spinal cord tumours (known as central nervous system tumours (CNS)) are the most common type of solid tumour in children, constituting about 20% of all cancers in patients under the age of 151. There are many different types of brain tumours; they occur at different ages, locations and with different abilities to grow, and propagate, both locally and at a distance.
A normal brain and spinal cord are composed principally of neurons (the “thinking part”) and glial cells (the “cement” that keeps neurons together). When neuronal cells are the starting point for a tumour, we call them embryonal tumours (i.e. medulloblastoma). When glial cells turn into a tumour, we call them gliomas. There are several different types of gliomas. Their classification is based on a number of criteria. Some of these include symptoms at presentation, the radiologic characteristics at the diagnostic imaging, the aspect of the lesion under the microscope, the molecular analysis of the lesion, etc.