Cancer.
There are few words in the English language that carry as much weight as cancer.
It is so terrifying that people don't want to speak its name. They call it the "Big C."
Some experts argue that our fear of cancer actually makes the problem worse. The more people know about cancer, the more they can do to prevent it or detect it early enough to get effective treatment. Many forms of cancer can be between if caught early enough.
So, what is cancer?
First of all, it is not just one disease. There are over 200 different types of cancers that occur in the human population and they essentially fall into five major categories:
Carcinomas attack the body's epithelial cells lining our organs.
Sarcomas are cancers of the supportive tissues such as muscles and bones.
Leukemias destroy bone marrow where blood cells are produce.
Lymphomas grow in the lymphatic system - part of our immune system.
Adenomas are cancers of glandular tissues such as the pituitary and thyroid glands.
No one is absolutely sure when the first cancers occurred but it was likely shortly after the first multicellular organisms appeared in the environment.
Cells need to communicate and cooperate in order for a multicellular creature to form. Cancer is, in part, a breakdown of the whole cooperate and communicate paradigm. Cancer is a consequence of being a multicellular organism and pretty much anything that is multicellular can develop cancer.
We know dinosaurs had cancer. There is a 150 million year old bone in the Carnegie Museum in Pittsburgh with remnants of a tumour preserved in it. The oldest evidence of cancer in primates is a four million year old bone tumour in a specimen of Australopithecus - our many times great ancestor.
Egyptian papyri from the 16th century BCE describe various types of tumours along with the treatments such as surgery and cauterization. The term cancer dates from the Greek father of modern medicine, Hippocrates (460-370 BCE), who described benign tumours as "oncos" or swellings and malignant tumours as "carcinos" or crabs because mature tumours are shaped like roundish blobs with radiating arms.
Cancer has been around for a very long time. It is not something new nor is even confined to animals.
Plants can get cancer. Or, at least, plants get something akin to cancer with uncontrolled cell growth resulting in galls. However, as plants do not have a well-developed circulatory system, plant cancers can't metastasize or spread throughout the body and are not usually fatal.
The circulatory system in animals allows cancer cells to spread throughout the body which is why early detection is important.
One of the apocryphal stories about cancer is some animals, such as sharks, don't get it and hence eating shark cartilage is a cure. Not true. Sharks do get cancer and shark cartilage doesn't have any significant medicinal properties.
But I haven't really answered the question of "what is cancer?"
Simply put, it is cell damage that results in mutated DNA which, in turn, causes the cell to lose its ability to self-regulate its division process. The cell divides uncontrollably until it becomes a mass that starts to impact the function of the body's organs or it metastasizes and spreads throughout the body affecting a variety of organs.
It is really that simple - and that terribly, terribly complicated.
For cancer to occur, a wide variety of things have to go wrong beyond just the damage to the DNA. After all, DNA is damaged every single day by light and by chemical compounds such as the food that we eat and the air that we breathe. Oxygen, essential for life, damages DNA under the right circumstances.
Furthermore, your body creates somewhere in the neighbourhood of 300 million new cells every minute - all without incidence or problems. Why do some cells turn cancerous?
Cell replication is a very controlled process with lots of checks and balances to ensure that nothing goes wrong. There are editing proteins that run up and down strands of DNA looking for mistakes. When they come across one, they fix it.
If they can't fix it, then they can trigger an action called apoptosis, or programmed cell death. In essence, the cell is told to commit suicide and it does. On top of this, each piece of DNA carries a telomere which shortens with each replication and effectively puts a limit on how many times that a strand of DNA can be copied. And if none of that works, there are cells in the body that specifically hunt down cancerous cells and destroy them.
All in all, a great many things have to go wrong from a biochemical point of view for cancer to occur. And yet it does which is why cancer is a scary word.
