Cells with mutated DNA.

Cancer is described a multitude of cells that grow outwith normal control.

This is a way of looking at how cancer occurs.
In the cell cycle there are lots of checkpoints or "pit-stops" where the cells are checked to ensure they are growing appropriately. For example there is one between the G1 and S phase of the cycle. Cyclin dependent kinases (CDK) are produced which allow the cell to move to the next stage if there is no DNA damage. If DNA damage is detected then the cell can either be halted in the cell cycle via CDK-inhibitors or it can be killed via apoptosis. Loss of these checkpoints and the proteins involved in signalling any damage (such as p53-a tumour suppressor gene) means that abnormal cells are able to continue growing and dividing and accumulate resulting in tumour formation and cancer.

Hope this is explained ok for you 8)

The way I look at it is that cancer is a tumor (abnormal growth/swelling) that has entered metastasis.
Metastasis means it is invasive to other tissues (such as the blood stream). Cancer is tumor, but tumor isn’t necessarily cancer.

I could be wrong.

how does cancer affect you? does it hurt or.. i never really understood wat happens, and how do you tell if you have it?

Awhile back, I had the rare privilege of attending a Cancer research seminar at UCSD Center for Excellence—thanks to one of my biology professors.
It was explained that cancer was a mutation in the DNA of a human cell. That is to say, the DNA which is like an instruction that tells a cell how to duplicate itself has a faulty instruction, which in turn a cell duplicates itself with an error or mutation—this can be compared to building a Toyota pickup truck using blueprints for a Ford Ranger. The mutated cells are now providing the blueprints for future cells. These mutated cells begin to multiply at an exponential rate thus forming a tumor. If doctors could detect these mutated cells prior to the proliferation of a tumor, a person would have a better chance of being cured by treatments like chemotherapy. This is not the case however; as mutated cells are at the microscopic level, and cancer is usually undetectable until it has grown into macroscopic size, at which point much damage has already been done.
To make matters worse, no cancer mutation is the same from person to person, as the combinations of DNA deviation is in the billions. It is like the way people make salad, one person puts cucumbers and carrots, while another person only uses bacon bits. The reason this is important is that one can then realize how problematic detection becomes. With all these variations, symptoms will not be the same, but I have known people who had cancer, and they experienced great pain.

yes, cancer can be very painful…

multiple mechanisms:

1) tumours have ways of inducing inflammation via release of many inflammatory mediators (cytokines, prostaglandins, leukotrienes) -> thus inflammatory pain

2) the tumours can damage activate and damage sensory nerves -> neuropathic pain

3) tumour can grow in a confined space (e.g. a growing tumour in a confined space like the brain or spinal cord)

however, it is not a rule that cancer is a painful death. Many people have malignant cancers or large benign tumours and have no pain. it depends on where the tumour is.

for example, i don’t think visceral tumours are the painful relative to other cancers since many of your internal organs are not well innervated by pain fibres.

ps. michaelxy… there is no clinical interest in trying to detect microscopic tumours and i doubt there ever will be… many people have microscopic tumours, however, over 99% of these never develop a blood supply and remain as microscopic tumours that will never grow beyond 1mm in size… thus most can stay small and be detected and cleared by our immune system… the reason why the vast majority of tumours never grow beyond microscopic is that they are severely hypoxic and in order to grow futher the need to induce our bodies to supply the tumour with blood… this is very hard to do for a tumour to induce angiogenesis and so most never make it and lie dormant for years… there are also many stages a cancer will go through before they become macroscopic – it isn’t as simple as continuous proliferation of cells… certainly not all cancers proliferate exponentially… as for treatment the only cancers we have a good hope of ‘curing’ with chemotherapy and radiotherapy alone is testicular cancer and leukaemia… but i think it’s still pretty true that surgery is the only way to cure cancer for most cancers and if that doesn’t work then the tumour eventually kills you..

Well at the seminar that I attended, the main focus of the discussion was using nano-technology, for the very purpose of detecting cancer in it’s early stages. I found a video that explains.
http://www.nsti.org/BioNano2005/symposi … rid=wmv_hi