What is Cancer?

Cancer is a general term used for a group of disorders, which manifest in most cases as an abnormal mass/lump/swelling formed due to abnormal cells that multiply uncontrollably, and which have the potential to invade other tissues, both local and distant.

Our body is a well-organized collection of trillions of small structures called cells. Cells are the structural and functional unit of living tissue. They are to a living tissue, what an atom is to an element or a molecule to a compound.

It is estimated that, in an adult human body, there may be anywhere between 50 to 75 trillion cells. But, how much is a trillion? A thousand billion makes a trillion; an unimaginably large number.

To understand the enormity of this figure, let us suppose you start counting each one of the cells in your body at a rapid rate of 50 to 75 cells per second; how long do you think you will take to finish counting?

Well, without taking any sort of break, including for food or sleep, it would take you 31,688 long years! Clearly, our body is an incredibly complex biological machine made of these trillions of parts.

In a normal human being, each one of these trillions of cells responds and functions according to the needs of the body. A group of cells form a tissue or an organ.

Depending on the tissue or the organ, cells are of different types. Normally, these cells grow, divide and form new cells, or die, as per the physiological needs of the body.

In other words, in a healthy person, the body controls the growth and multiplication of the cells according to their needs, and the cells strictly comply with these rules.

In a normal adult, about 3 million red blood cells die every second while at the same time the remaining tissues of the body lose about one million cells!

These are constantly replaced by the formation of new cells. The new cells formed are almost exact copies of the ones that have died, and they take over the function of these lost cells.

Unusually, a new abnormal cell is created, which fails to obey the strict control on cell growth, multiplication and function.

This happens due to some permanent alteration in the cell’s genetic material – the DNA, either spontaneously or due to the influence of chemicals, radiation, etc. This process is known as a mutation.

Considering the huge production of new cells in the body every second, it is a marvel that this event is very rare. This is because there are highly efficient ‘proofreading’ mechanisms, which check for errors in the formation of the new DNA and remove them.

(Here, it is important to know that mutations are not always bad. In fact, we owe the evolution of our entire biological world from a single-celled organism into the biodiversity around us, including ourselves, largely to mutations. The mutation is basically a change in the DNA which escapes the ‘proofreading’ system and therefore, becomes established in the genetic code of that cell and can hence then be passed on to its daughter cells when it divides and multiplies. Some of these mutations can give rise to the formation of a tumor cell.).

This abnormal mutant cell, instead of responding to the needs of the body, starts to grow and multiply in an uncontrolled manner.

This gives rise to the formation of more abnormal cells, and since these are copies of the original mutant cell, they behave exactly like the parent cell, i.e. they too, in turn, grow and multiply uncontrollably; this cycle keeps continuing with every new generation of abnormal cells.

This event is thus like a chain reaction that eventually leads to the formation of a lump or a swelling, which is called a tumor or tumour.

These mutant cells, and the tumor tissue formed by them, are also abnormal in their structure, architecture and function. They grow more rapidly and uncontrollably, as compared to the normal cells and tissues around.

Thus they affect the body in several ways. They take away nourishment from the normal tissues and grow at their expense. Tumor tissue is not normal tissue and therefore, it does not serve the function of the tissue it was supposed to be.

And since they grow uncontrollably, they invade the space occupied by the normal tissues and replace them, thus compromising their function. However, all tumors are not cancers.

An important behaviour, which is the hallmark of cancer, is the ability to spread from the organ or tissue of origin, to other parts of the body.

This is the most dangerous characteristic of cancer. Cancer is thus a general term used for a group of disorders, which manifest in most cases as an abnormal mass/lump/swelling formed due to abnormal cells that multiply uncontrollably, and which have the potential to invade other tissues, both local and distant.