Question: why is cancer so harmful and why cant doctors find it at an early stage even if you have had tests?

Angela Stokes answered on 13 Nov 2014:

Hi there Melon
It is unusual for doctors to look for a cancer and not find it even at early stage – we hear about a few that are misdiagnosed but there are thousands more that get diagnosed early. Having said that there are many cancers which at an early stage do not have any symptoms, or the symptoms are similar to those of other diseases, or often in the case of children they can’t describe how they are feeling so it is often difficult for doctors.

There are many types of cancer, some grow quickly and some grow slowly – quickly growing cancers are in general more difficult to treat. There are four main stages. In stage one the cancer cells stay in one location, this might be the breast for example this is an early stage cancer. The tumour could then spread to other parts of the body, which we call stage two. When the it has spread to muscles we call this stage 3 and when organs such as liver and kidneys are involved it is called stage 4 – this is usually fatal. One way to look at cancer is to imagine it as a weed which is gradually destroying a garden. The weeds take up space and use nutrients and kill off healthy plants….and when you have got rid of it there is also a possibility of it coming back.

So what happens exactly? Well in simple terms, something causes the DNA in a cell to become damaged, this causes it to reproduce too fast, and all of the new cells have the same DNA damage so they all reproduce too fast too, and so you have a fast growing ball of cells which is out of control – a tumour. This tumour will put pressure on any body parts or organs nearby and damage them – or if it infiltrates the organ it can be deadly.